Operating Cost of Single versus Twins

markpierce · Jun 15, 2022

Didn't the era of recreational trawlers (diesel boats never, not able, exceeding hull-speed) begin with the fuel crises of the mid-1970s? Are we returning? (I've always "been there".)

catalinajack · Jun 15, 2022

Simi 60 said:
We have seperate starts with both alternator and smart charger attached to keep them in peak condition.

At the flick of a switch we can get a boost using the house bank if required.

Yes I do know.

Thank you for making my point.

catalinajack · Jun 15, 2022

Bryant said:
All great questions. One of my major criteria when buying my boat was 1 engine.

Backing a single screw boat takes practice but you can learn it easily.

One engine has 1 motor, 1 transmission, 1 shaft, 1stuffing box, 1 cutless bearing and the screw is protected by the the housing that holds the shaft and screw.

Two engines don’t have that.

I have my motor, transmission, shaft,cutless bearing and gen professionally maintained. A professional will find issues you will never see if you do it yourself. Just a standard annual maintenance with no issues will be $1000. Double that for 2 engines. When it’s time for serious maintenance, replacement or repair you are looking at thousands for two engines.

With one engine you can literally move around the motor and transmission with ease. With 2 motors you can barely get into the engine room.

The myth that two engines are more reliable than one is tempting but doesn’t hold water. A well maintained Diesel engine will probably only fail for 1 reason; fuel. If you have bad fuel you can have 2 engines or 10.

They will all fail. I have one engine with 7700 hours and it purrs like a kitten. This is my advice. I’m a one engine guy. Listen to all advice and make your decision.

Stay away from Volvos. Expensive to maintain and very difficult to get parts. I have 50 years boating experience, for what it’s worth.

A Ford Lehman 120 burns 2 gals/hr at 8 kts in calm seas.

Your statements are woefully flawed generalities that do no apply to all twin-engined boats. You prefer a single but having a second engine for redundacy is no myth; it is common sense. I own a DeFever 44. Here are some examples.

1. My screws are not unprotected. Their bottoms lie four inches ABOVE the full length keel.

2. Yes, engines themselves seldom fail but that is not the only cause of lack of propulsion. Twice, at very inopportune times, I lost propulsion because of a failed DriveSaver coupling. First was in the stair step locks in Ottawa. No propulsion in a single there would not have been fun for anyone especially because it was Canada Day. The second time forced me to run on one engine 45 miles to my destination. The TowBoat US boat was unable to tow me any distance. And it was Christmas Eve. Not fun. If I had had only s single, I would have been stuck there for a few days.

What else could stop an engine? Failed vibration damper. Blown hoses. Fuel pump. Starter (leaving an anchorage). Fan belt and you forgot the spare. The list goes on so to say that a single gives one just as much peace of mind as do twins is ridiculous. It is a choice made with known risks.

3. Bad fuel, a rarity, can be mitigated with dual Racors. So, having both engines stop cuz of bad fuel happens only from bad boating.

4. Engine room access. Mine is 5.5 feet tall and I can access the outboard sides of each with little difficulty.

5. My 6,700 hour Lehman 120s purr as your does.

6. Standard annual maintenance on a Lehman 120 is $1,000? Now that is one of the most ridiculous assertions that I have ever read on this forum. Let's see. Oil, three gallons, $50. One oil filter, $15. One impeller, $40. One fuel filter, $40. What have I missed that will get to $1,000?

7. Learning a single screw - yes, one can learn, but nearly as easily and quickly as with twins. And, when conditions go to crap, twins outshine singles every time.

ranger58sb · Jun 15, 2022

JYoung said:
If you know what you are doing, single is the advantage every step of the way. Today, so many seem to need thrusters. Do not understand why. If you know how to drive a boat and you know what you are doing, single is a snap. As far as cost, efficiency and overall value, one engine is all you need.

I guess you won't be coming back, but I'll just mention you used two IF statements... both assuming already-existing stellar knowledge and experience with a single screw boat.

Some folks who ask questions in forums don't already have that in their tool box, often hence their questions.

IOW your answer assumes a level of experience the questioner may not have yet.

-Chris

rslifkin · Jun 15, 2022

markpierce said:
Didn't the era of recreational trawlers (diesel boats never, not able, exceeding hull-speed) begin with the fuel crises of the mid-1970s? Are we returning? (I've always "been there".)

Yup, that's definitely what spurred the era of recreational trawlers becoming more common. But many of them have never been truly displacement hulls. A lot of the TTs and such never had enough power to get very far above hull speed, so as a practical matter, they rarely did, but they were capable of exceeding it.

The important part is that anything that would be considered a trawler is intended to spend a lot of its time cruising slowly and efficiently (and with acceptable low speed handling). Even if it can go faster. In great contrast to many faster powerboats where going fast is the priority and low speed handling is poor enough that you'll never do it outside a no wake zone.

mvweebles · Jun 15, 2022

catalinajack said:
Your statements are woefully flawed generalities that do no apply to all twin-engined boats. You prefer a single but having a second engine for redundacy is no myth; it is common sense. I own a DeFever 44. Here are some examples.

1. My screws are not unprotected. Their bottoms lie four inches ABOVE the full length keel.

2. Yes, engines themselves seldom fail but that is not the only cause of lack of propulsion. Twice, at very inopportune times, I lost propulsion because of a failed DriveSaver coupling. First was in the stair step locks in Ottawa. No propulsion in a single there would not have been fun for anyone especially because it was Canada Day. The second time forced me to run on one engine 45 miles to my destination. The TowBoat US boat was unable to tow me any distance. And it was Christmas Eve. Not fun. If I had had only s single, I would have been stuck there for a few days.

What else could stop an engine? Failed vibration damper. Blown hoses. Fuel pump. Starter (leaving an anchorage). Fan belt and you forgot the spare. The list goes on so to say that a single gives one just as much peace of mind as do twins is ridiculous. It is a choice made with known risks.

3. Bad fuel, a rarity, can be mitigated with dual Racors. So, having both engines stop cuz of bad fuel happens only from bad boating.

4. Engine room access. Mine is 5.5 feet tall and I can access the outboard sides of each with little difficulty.

5. My 6,700 hour Lehman 120s purr as your does.

6. Standard annual maintenance on a Lehman 120 is $1,000? Now that is one of the most ridiculous assertions that I have ever read on this forum. Let's see. Oil, three gallons, $50. One oil filter, $15. One impeller, $40. One fuel filter, $40. What have I missed that will get to $1,000?

7. Learning a single screw - yes, one can learn, but nearly as easily and quickly as with twins. And, when conditions go to crap, twins outshine singles every time.

CatalinaJack - still have your DriveSavers?

Annual maintenance on a yacht-diesel by a professional does approach $1k. A decent mechanic @ $150/hr will do much more than change oil and an impellor - valve adjustment, engine alignment, sea-strainer, battery check, lube cables/linkages, adjust idle RPM, check hoses, check/replace belts, check/clean heat exchanger, etc. Much of the stuff needed to keep an engine running reliably. There is some efficiency of labor with twins, so it's not 2x, but it's not trival either.

The Defever 44 is fairly unique in its twin configuration. On the outside, sort of looks like a traditional Taiwan Trawler/Sundeck. Clearly, it's not - as you mention, stand-up engine room, smaller engines sized for displacement speeds, decent access to outboard side of engines, I love the sea-chest, etc. It's a solid boat that's a sleeper in the market. The boat has a fair amount of sail area that can make close-quarter maneuvering a handful, and really needs some form of active stabilization. But it's a solid boat. I wish there were more twins like it in the sub-60' trawler segment.

As a devout single guy, I try to be realistic and objective. Clearly, there is some benefit to have a twin for redundancy. But that's mostly for distance cruising where there is zero support. The situations you describe are highly inconvenient, but salvagable. Keep your engine well-maintained and liklihood of underway failure is pretty slim. And lets not forget that while you may get home if one of your engines fail, it will hobble you until it gets fixed (I know of no one who would continue their cruise/vacation with only one of two engines working). And you have twice the liklihood of that happening, especially when you consider twins are rarely as well maintained as singles.

Peter

Art · Jun 15, 2022

mvweebles said:
As a devout single guy, I try to be realistic and objective. Clearly, there is some benefit to have a twin for redundancy. But that's mostly for distance cruising where there is zero support. The situations you describe are highly inconvenient, but salvagable. Keep your engine well-maintained and liklihood of underway failure is pretty slim. And lets not forget that while you may get home if one of your engines fail, it will hobble you until it gets fixed (I know of no one who would continue their cruise/vacation with only one of two engines working). And you have twice the liklihood of that happening[/U], especially when you consider twins are rarely as well maintained as singles.

Peter

I'm sorry Peter... cause I always enjoy reading your posts... but, I just gotta mention... portion of this paragraph is, well - just too much! LOL

The platitude that "... twins are rarely as well maintained as singles." is simply a wishful guess by single engine advocates searching for something else detract-full to say about boat owners who enjoy twins.

Your mention of "... (I know of no one who would continue their cruise/vacation with only one of two engines working). "And you have twice the likelihood of that happening..." WOW - That' a mixed-up bag of a statement if I've ever seen one. Our Tolly tracks well on one engine at below hull speed and its BW Velvet Drive trany can free wheel with no problem. Your mention of: "... you have twice the likelihood of that happening..." Gee Peter... you have once the likelihood of that happening, and, if it does you're dead in the water! Twins are NOT!

Please understand, I'm not trying to bad mouth single engine boats... but, I'm tired of single engine owners too often trying to put a bad slant on twins.

I've owned and enjoyed both types of boats and feel they both have their high and low points for ownership. As Rodney King said: "Can't we all just get along!"

Happy Boat-Ownership Daze! - :speed boat:

rslifkin · Jun 15, 2022

With twins, you have a higher risk of having a failure, but a lower risk of being stranded due to a failure.

Personally, I wouldn't worry all that much about the redundancy unless crossing oceans or spending a lot of time in confined waters. In confined waters a failure can be a big deal if you lose all propulsion. But in somewhat more open waters, it's not such a big deal to drop the anchor (if reasonable), get to work on the problem, and call for a tow if you can't fix it.

mvweebles · Jun 15, 2022

Art said:
I'm sorry Peter... cause I always enjoy reading your posts... but, I just gotta mention... portion of this paragraph is, well - just too much! LOL

The platitude that "... twins are rarely as well maintained as singles." is simply a wishful guess by single engine advocates searching for something else detract-full to say about boat owners who enjoy twins.

Your mention of "... (I know of no one who would continue their cruise/vacation with only one of two engines working). "And you have twice the likelihood of that happening..." WOW - That' a mixed-up bag of a statement if I've ever seen one. Our Tolly tracks well on one engine at below hull speed and its BW Velvet Drive trany can free wheel with no problem. Your mention of: "... you have twice the likelihood of that happening..." Gee Peter... you have once the likelihood of that happening, and, if it does you're dead in the water! Twins are NOT!

Please understand, I'm not trying to bad mouth single engine boats... but, I'm tired of single engine owners too often trying to put a bad slant on twins.

I've owned and enjoyed both types of boats and feel they both have their high and low points for ownership. As Rodney King said: "Can't we all just get along!"

Happy Boat-Ownership Daze! -

I think rslifkin's post just before this one says what I was trying to say more eloquantly - twins have higher probability of failure; but lower chance of being stranded (impact).

The reason for my statement that owners of singles' are more diligent has it's roots in Mark Twains adage "if you put all your eggs in one basket.....watch that basket!" But I shouldn't have made such a declarative statement that all twin owners are less festidious than owners of a single. I will say that there is more incentive for a single-owner to tag all bases.

I have tried hard not to put a bad slant on twins. You will never hear me say a single handles as well as a twin in close-quarters. It just isn't true. You will never hear me say a single is as reliable as twin because that just isn't true either (duh). You will never hear me say you can put a single anywhere you want because that isn't true (at least for me).

Now, I've owned a twin (back in the early 1990s I owned a 1975 Uniflite ACMY with Cummins 555s). The stuff you won't hear me say about twins includes: "maintenance costs are close to the same." "Fuel economy of a twin is roughly the same as a single when operated at displacement speeds" (the difference may be acceptable, but there is a decent penalty). "Running a twin on one engine is similar economy to if it was a single" (see previous).

To my tastes, the #1 reason to own a twin is you can fit more horsepower in the engine room so you can faster. #2 reason is maneuverability. #3 reason is redundancy (distant #3 for vast majority of people who never leave TowBoatUS zone).

The reasons to own a single are a bit less clear because it bleeds into reasons to own a displacement boat which is hard for me to differentiate because I just like going at jogging speed. But if I were to compare buying a single or twin GB36, I would chose a single due to #1 engine room accessibility/maintainability; #1a would be economy (and range). #2 is protected running gear; #3 (distant benefit) is ability to carry other stuff and equipment such as generator, watermaker, etc.

Calculus really chnages if you're headed into remote zones. I still do it with a single, and believe me, I check my running gear, hoses, etc. I mean I really go through it - replace pumps vs rebuild, etc.

Apologies if I was somewhat hyperbolic, but there was certainly a kernal of truth.

Peter

O C Diver · Jun 15, 2022

One of the things to consider in the single or twin engine discussion would be the Lindbergh theory. Crossing the Atlantic once in a single engine plane has a reasonably high expectation of success as far as engine failure is concerned, because it's once with an extremely low percentage of the engine's life expectancy. The more times you do it and the greater the engine's percentage of life expectancy, the more likely it is that you will die.

To extrapolate this to boats:
If you consider the percentage of time that a single engine failure would put you in a life threatening position, for the average forum person, the percentage is probably exceeding small. Now if you plan to cross oceans or spend much of your time in remote areas, that percentage of operation in riskier areas may exceed your comfort level.

For my cruising, I view life threatening engine failure at about 1 to 2 percent of underway cruising. I can accept that level of risk.

Ted

BandB · Jun 15, 2022

Wifey B:

Case solved. 6. #^%# I need more. We only have 3.

Nomad Willy · Jun 15, 2022

Ted wrote;
“For my cruising, I view life threatening engine failure at about 1 to 2 percent of underway cruising. I can accept that level of risk.”

But Ted if you die on a 1% chance you’re still dead.

Re boats Ted wrote;
“To extrapolate this to boats:
If you consider the percentage of time that a single engine failure would put you in a life threatening position, for the average forum person, the percentage is probably exceeding small. Now if you plan to cross oceans or spend much of your time in remote areas, that percentage of operation in riskier areas may exceed your comfort level.”

OK fine.
I boated for 20+ years in SE Alaska and only came close to death twice. Once due to terrible weather and once due to near engine failure.
Was rounding Cape Caution when the single engine slowed gradually down to an idle .. for about two minutes. That was a big two minute pucker factor for me and I don’t wann’a repeat it. The engine slowly came back up to cruise rpm but we were very close to the rocks on the Cape. We did the pan-pan and there were several other boats fairly close. Would’a been much safer if we had been further out but it shows the faith I had in my engine .. faith that I no longer have.

Please share you’re high pucker experience when you have it. If you're around.

O C Diver · Jun 15, 2022

Nomad Willy said:
Ted wrote;
“For my cruising, I view life threatening engine failure at about 1 to 2 percent of underway cruising. I can accept that level of risk.”

But Ted if you die on a 1% chance you’re still dead.

Re boats Ted wrote;
“To extrapolate this to boats:
If you consider the percentage of time that a single engine failure would put you in a life threatening position, for the average forum person, the percentage is probably exceeding small. Now if you plan to cross oceans or spend much of your time in remote areas, that percentage of operation in riskier areas may exceed your comfort level.”

OK fine.
I boated for 20+ years in SE Alaska and only came close to death twice. Once due to terrible weather and once due to near engine failure.
Was rounding Cape Caution when the single engine slowed gradually down to an idle .. for about two minutes. That was a big two minute pucker factor for me and I don’t wann’a repeat it. The engine slowly came back up to cruise rpm but we were very close to the rocks on the Cape. We did the pan-pan and there were several other boats fairly close. Would’a been much safer if we had been further out but it shows the faith I had in my engine .. faith that I no longer have.

Please share you’re high pucker experience when you have it. If you're around.

Ok, I guess you missed the point. 1 to 2% of my time underway would be possibly life threatening if the motor quit. Right now there are 3 knot currents in some parts of the Trent Severn Waterway. Losing the engine and going to the spillway could be life threatening. But it hasn't happened. So I have no life threatening stories.

In 4,100 hours, I've had one engine shutdown for about an hour. It was on a large placid lake. I drifted until I got going again.

My point was that having an engine shutdown at a point when it would be life threatening for me is extremely unlikely.

Ted

BandB · Jun 15, 2022

O C Diver said:
Ok, I guess you missed the point. 1 to 2% of my time underway would be possibly life threatening if the motor quit. Right now there are 3 knot currents in some parts of the Trent Severn Waterway. Losing the engine and going to the spillway could be life threatening. But it hasn't happened. So I have no life threatening stories.

In 4,100 hours, I've had one engine shutdown for about an hour. It was on a large placid lake. I drifted until I got going again.

My point was that having an engine shutdown at a point when it would be life threatening for me is extremely unlikely.

Ted

To extrapolate. If OCD sees a 1% of his time that an engine failure would be life threatening and then has has failure 1 of 4100 hours so 0.024% then you multiply those and his life risk is less than 1/1000'th of a percent. So 2 in 1,000,000 or something like that. 1 in 500,000 or 121 times his lifetime boating. Maybe none of this is accurate though.

I've never been in a situation where loss of engines would have been life risking, nor have I ever lost engines. We do everything we can to minimize risk and would do so regardless of the number of engines.

While I am more comfortable with twins, I have no disagreement with those who use singles. We have at least two engines on all boats, but we don't own a boat that was ever offered with singles. If we were purchasing many of the boats owned by others here, we'd be perfectly happy with their singles or twins, just as they are. Builders pair engines to boats well. There are ways to minimize the negatives of either singles or twins through planning and other equipment.

As to cost, twin 200 hp vs. single 400 hp would be very little different, but that kind of offering is so rare and then you're into all the other factors. Find the boat package that works for you and then figure out how to offset any negatives you perceive.

Hippocampus · Jun 15, 2022

Have spent a fair amount of time on passage, in remote areas, in areas where there was neither skilled wrenches nor parts availability.
The focus here is on engines but single point failures occur on sailboats and both.
For sail-masts, spreaders, standing rigging, winches etc.
For both -steering, windlass, ground tackle, watermakers, frig/freezers, AP, nav, comm, etc.
As well as PASSIVE ways to face survival weather
Sail or power a blue water/remote voyaging boat needs to be designed and outfitted from the ground up for that service. Simple things like a suitable workroom, ample storage for tools and parts. Redundancy of ALL key systems or designed in workarounds. Engine(s) are the least of it but for reasons I don’t fathom seemly always the focus of these discussions. Personally have seen innumerable cat A boats I would not consider BWBs. To function function in that setting there’s a lot more than just stability curves or range.
Look at any of the production voyaging boats or the list in the appendage of Beebe’s book. Majority are singles wth or without some form of get home. Where they differ from coastal boats are in all the others features that are necessary for a functioning BWB.
I sailed a boat with a single mast and one engine. I have friends who have lost the stick, steering, engine and have suffered major damage from boarding waves. Believe in a voyaging boat built for that purpose feel handling and filtering and independent tanks and all the other features that decrease risk of failure are part of the initial package. Risk lies elsewhere.
I think with a twin I’d still call for a tow. Wouldn’t be too excited about trying to do close quarters handling on a twin with one functional engine. On a twin or single if I lost power think I’d drop the hook. See if I could sort myself out. I can anchor in anything under 60’ at 5:1. As vessel n distress I’d have more opportunities to do so.
Seems there’s a mix of coastal and blue water/remote thinking among some. Think coastally I’m more likely to wrap a shaft or have something bend a prop for the type of coastal boating I currently do than lose the engine.
Boats don’t auger in like planes. I’m not doing 2000nm non stop like I once did. I just blew big boat bucks having multiple details of the running gear and engine brought to perfection. So look at these conversations like the pt. bought into the ED with a gunshot wound and a stabbing. First thought is to focus on the GSW. But the stab wound nicked his aorta. Little exterior blood but that’s what will kill him.

Nomad Willy · Jun 15, 2022

Ted I don’t think I missed your point but what you describe as going over a spillway is true you’re much more a risk taker than I.

rslifkin · Jun 15, 2022

Hippocampus said:
I think with a twin I’d still call for a tow. Wouldn’t be too excited about trying to do close quarters handling on a twin with one functional engine. On a twin or single if I lost power think I’d drop the hook. See if I could sort myself out. I can anchor in anything under 60’ at 5:1. As vessel n distress I’d have more opportunities to do so.
Seems there’s a mix of coastal and blue water/remote thinking among some. Think coastally I’m more likely to wrap a shaft or have something bend a prop for the type of coastal boating I currently do than lose the engine.
Boats don’t auger in like planes. I’m not doing 2000nm non stop like I once did. I just blew big boat bucks having multiple details of the running gear and engine brought to perfection. So look at these conversations like the pt. bought into the ED with a gunshot wound and a stabbing. First thought is to focus on the GSW. But the stab wound nicked his aorta. Little exterior blood but that’s what will kill him.

Whether a twin with an engine out is worth a tow vs coming in on one will depend on the boat and weather conditions in my mind. There are definitely docking situations I wouldn't attempt with an engine out but others I wouldn't be concerned about in at least semi-reasonable weather.

Single or twin I'd generally be dropping the anchor to assess the problem (unless there was a better option only a short limp away). The big difference is, if you're in a narrow channel surrounded by rocks, a river with high currents, or other bad situation when the failure occurs (be it an actual engine failure, damaged running gear making 1 engine useless, etc.) the twin has the ability to maneuver to a safe spot to anchor while the single is going to be anchoring "right now" and hopefully avoid things going horribly wrong in the process. And if you can't fix the problem on the spot (such as needing a part you don't have), the single will need a tow, while the twin comes back to that decision process of "can I reasonably limp somewhere with this failure?" But that last bit is more a matter of convenience than anything.

As OC Diver pointed out, most of us spend relatively little time in situations where losing the engine on a single would put you in an imminently dangerous situation faster than you can drop the anchor. So single vs twin is rarely a safety decision unless crossing oceans or otherwise venturing beyond where you can be towed in.

Hippocampus · Jun 15, 2022

psneeld · Jun 15, 2022

My experience includes a lot of "what happens when you lose power and it is life threatening or potentially catastophic."

I agree it happens rarely.

But it happens a lot to even the best skippers and pristine vessels.

It forever changes some, but not all.

Like all risks, you can mitigate or not to your comfort level. The trick is to set your comfort level based on good, appropriate experiences....as pointed out, not everyone has the experience to be good at docking single engine vessels, and way more probably don't have the experience to extrapolate into potentially lethal situations.

I agree no need for twins all the time unless the convenience of "keep going" is really high.

Seevee · Jun 15, 2022

Hippocampus said:
Amen

Good point.... Get what works for you, and deal with it.

Marco Flamingo · Jun 15, 2022

Here is the official test of whether you should have a single or twin. Have somebody sneak up behind you and light a firecracker. If your pants are wet, you need twins.

Sorry, really sorry. Couldn't help myself. But the answer does seem to be based on one's level of anticipatory anxiety. That runs the gamut from "I'm bullet proof" to "The sky is falling," neither of which is good.

There may be an accurate twin vs. single risk/benefit calculation, but each individual will override that to a large degree with their own perception. Personally, I prefer a single so that when I die the inevitable tragic death when my single motor stops the "twinnies" can say "See, I told you." In the mean time, I've got extra $$$ in my pocket and can skip around in the engine room.

Art · Jun 16, 2022

Marco Flamingo said:
Here is the official test of whether you should have a single or twin. Have somebody sneak up behind you and light a firecracker. If your pants are wet, you need twins.

Sorry, really sorry. Couldn't help myself. But the answer does seem to be based on one's level of anticipatory anxiety. That runs the gamut from "I'm bullet proof" to "The sky is falling," neither of which is good.

There may be an accurate twin vs. single risk/benefit calculation, but each individual will override that to a large degree with their own perception. Personally, I prefer a single so that when I die the inevitable tragic death when my single motor stops the "twinnies" can say "See, I told you." In the mean time, I've got extra $$$ in my pocket and can skip around in the engine room.

Another perfect example of a fellow who risks death for a few extra bucks in his pocket! :lol:

BandB · Jun 16, 2022

Marco Flamingo said:
Here is the official test of whether you should have a single or twin. Have somebody sneak up behind you and light a firecracker. If your pants are wet, you need twins.

Sorry, really sorry. Couldn't help myself. But the answer does seem to be based on one's level of anticipatory anxiety. That runs the gamut from "I'm bullet proof" to "The sky is falling," neither of which is good.

There may be an accurate twin vs. single risk/benefit calculation, but each individual will override that to a large degree with their own perception. Personally, I prefer a single so that when I die the inevitable tragic death when my single motor stops the "twinnies" can say "See, I told you." In the mean time, I've got extra $$$ in my pocket and can skip around in the engine room.

Actually, the far more common reason for twins is added power and speed and has nothing to do with safety. Some do it for safety, but that's a minority. If you're looking to add some power to a 40'+ boat, often a bigger single engine just isn't a good option, but a second engine has tremendous advantages.

While this is true on planing and semi-planing or semi displacement, it's even true as size creeps up on full displacement. As an example, a Krogen 55 Expedition is standard with twin Deere 160 hp. Could it be built with a single 320 or so? Yes, but fit of engines and shafts and props is so much easier with the twins plus then the other arguments of redundancy.

We had a 44' Riva, daughter has it now. Twin 800 HP Mans. No way a 1600 HP engine could have been fit into that boat.

These discussions always evolve into safety, redundancy, and handling, but there are many more reasons including design. Ultimately, buy what appeals most to you and don't worry about justifying it to others or yourself.

catalinajack · Jun 16, 2022

mvweebles said:
CatalinaJack - still have your DriveSavers?

Annual maintenance on a yacht-diesel by a professional does approach $1k. A decent mechanic @ $150/hr will do much more than change oil and an impellor - valve adjustment, engine alignment, sea-strainer, battery check, lube cables/linkages, adjust idle RPM, check hoses, check/replace belts, check/clean heat exchanger, etc. Much of the stuff needed to keep an engine running reliably. There is some efficiency of labor with twins, so it's not 2x, but it's not trival either.

The Defever 44 is fairly unique in its twin configuration. On the outside, sort of looks like a traditional Taiwan Trawler/Sundeck. Clearly, it's not - as you mention, stand-up engine room, smaller engines sized for displacement speeds, decent access to outboard side of engines, I love the sea-chest, etc. It's a solid boat that's a sleeper in the market. The boat has a fair amount of sail area that can make close-quarter maneuvering a handful, and really needs some form of active stabilization. But it's a solid boat. I wish there were more twins like it in the sub-60' trawler segment.

As a devout single guy, I try to be realistic and objective. Clearly, there is some benefit to have a twin for redundancy. But that's mostly for distance cruising where there is zero support. The situations you describe are highly inconvenient, but salvagable. Keep your engine well-maintained and liklihood of underway failure is pretty slim. And lets not forget that while you may get home if one of your engines fail, it will hobble you until it gets fixed (I know of no one who would continue their cruise/vacation with only one of two engines working). And you have twice the liklihood of that happening, especially when you consider twins are rarely as well maintained as singles.

Peter

Peter, those DriveSavers are gone. If I ever acquired a boat that had them, they would be the first improvement (removal) I would make. In my post I did not mention how one of them failed. I gently ran aground on sand at Cayo Costa in Florida, a story in itelf. It should have been a simple matter of backing off the sandbar and it started off that way. The boat began to move and I applied more throttle to get her free. But, the plastic coupling ripped apart leaving me with just one engine. It was the morning of Christmas Eve day. The tow boat showed up to pull us off three hours later. No way he could have pulled our 56,000# boat 45 miles to port. We would have been stuck there for at least two days waiting for a more powerful tow boat. So, yeah, having another engine saved the day. We pulled into the Legacy Harbor Marina in Fort Myers in the dark.

Yes, a failed engine of two will hobble but a failed single stops one dead, IN PLACE. I fail to see your point on this one.

As far as the annual maintenance, implicit in my response was that the maintenance is done by the owner which is the case for many of us. Valve adjustments, engine alignments, idle adjustments are clearly not annual maintenance items. Sea strainers? Annually? How about maybe weekly. Belts? Maybe every three years at a cost of $15 each. I'll grant you the heat exchangers should be cleaned every couple of years. So, yes, if paying a technician, the cost is easily $1K. Doing the work yourself, the cost is pretty much insignificant. I should have made that distinction.

As for the distance cruising assertion, I wasn't distance cruising when that DriveSaver blew. But having that second engine got me to port safely where I could deal with the repair at my leisure. I would not ever choose to cruise on one engine but a lot of boaters do that regularly to save a bit of fuel. I couldn't be bothered but it is fairly easily done especially with Velvet Drive transmissions

The DeFever engine room, yes, it is not stand-up at just 5'5" tall but I can assure you it is of no consequence even to this 6'1" guy. Not much of the work there is done standing up. The DF44 is not the only boat with twins having good engine room access; to wit, some Marine Traders; Great Harbours, there may be others but the DeFevers are not unique in this regard. Now, Bayliners, Grand Banks 42s, not so much.

Twins rarely as well maintained as singles - please. As a member of the DeFever owners association I can assure you that DeFever owners are just as meticulous about maintenance as any single owner. And, I think this is true among most owners quite the opposite of rarely as you opine.

rslifkin · Jun 16, 2022

catalinajack said:
The DeFever engine room, yes, it is not stand-up at just 5'5" tall but I can assure you it is of no consequence even to this 6'1" guy. Not much of the work there is done standing up. The DF44 is not the only boat with twins having good engine room access; to wit, some Marine Traders; Great Harbours, there may be others but the DeFevers are not unique in this regard. Now, Bayliners, Grand Banks 42s, not so much.

Agreed. Good vs bad access is as much about the design of the boat and where equipment is placed as anything. On boats that were designed to be a single and later offered with twins, the access usually sucks because there's too much other stuff packed into the engine room. Same on boats that try to keep the fuel tanks, etc. centered lengthwise and use saddle tanks in the engine room.

Even in the low height engine rooms (like mine at about 3'6") access varies a lot. I've seen some pictures on here of boats with tanks jammed up against engines and other stuff that makes them a nightmare to navigate. Big difference compared to the pictures I posted earlier where the biggest issue is the slightly awkward crawl across the stringers, etc. to get to the area you need, then you just kinda sit down and work on stuff (as there's plenty of space around the engines in every direction).

catalinajack · Jun 16, 2022

rslifkin said:
Whether a twin with an engine out is worth a tow vs coming in on one will depend on the boat and weather conditions in my mind. There are definitely docking situations I wouldn't attempt with an engine out but others I wouldn't be concerned about in at least semi-reasonable weather.

Single or twin I'd generally be dropping the anchor to assess the problem (unless there was a better option only a short limp away). The big difference is, if you're in a narrow channel surrounded by rocks, a river with high currents, or other bad situation when the failure occurs (be it an actual engine failure, damaged running gear making 1 engine useless, etc.) the twin has the ability to maneuver to a safe spot to anchor while the single is going to be anchoring "right now" and hopefully avoid things going horribly wrong in the process. And if you can't fix the problem on the spot (such as needing a part you don't have), the single will need a tow, while the twin comes back to that decision process of "can I reasonably limp somewhere with this failure?" But that last bit is more a matter of convenience than anything.

As OC Diver pointed out, most of us spend relatively little time in situations where losing the engine on a single would put you in an imminently dangerous situation faster than you can drop the anchor. So single vs twin is rarely a safety decision unless crossing oceans or otherwise venturing beyond where you can be towed in.

Docking a boat, at least my DeFever, with one engine is hardly different than docking a single screw boat, regardless of conditions. It merely requires a bit more or less rudder input depending. This especially true if the boat has a bow thruster. I have twice brought our boat into difficult marinas on one engine with no angst.

Oh, here is another personal anecdote. This one is, indeed fuel-related. I once had an injector hard pipe crack. Had to shut down that engine. It was almost dark. We docked on someone's T-head, in heavy wind, in the dark. As we had a full set of six spares on board we installed a new one the next morning. We had first tried setting our anchor. In that particular place, apparently a rock hard bottom, our anchor would not take a set. We were hopelessly dragging toward disaster. So, to say that simply drop anchor and wait for a tow, well, not always a solution. Another difficult situation when the day was saved by having a second operational engine.

rslifkin · Jun 16, 2022

catalinajack said:
Docking a boat, at least my DeFever, with one engine is hardly different than docking a single screw boat, regardless of conditions. It merely requires a bit more or less rudder input depending. This especially true if the boat has a bow thruster. I have twice brought our boat into difficult marinas on one engine with no angst.

Oh, here is another personal anecdote. This one is, indeed fuel-related. I once had an injector hard pipe crack. Had to shut down that engine. It was almost dark. We docked on someone's T-head, in heavy wind, in the dark. As we had a full set of six spares on board we installed a new one the next morning. We had first tried setting our anchor. In that particular place, apparently a rock hard bottom, our anchor would not take a set. We were hopelessly dragging toward disaster. So, to say that simply drop anchor and wait for a tow, well, not always a solution. Another difficult situation when the day was saved by having a second operational engine.

I've docked on one as well. The biggest issue with my boat is that you have very limited ability to back up with an engine out. You can do it with enough back and fill, but not if there's much wind. There's just too much prop walk and the thrust is too far off center. Maneuvering forward is, as you pointed out, not much worse than most singles, so that part is no problem. Just have to remember that if going straight the rudders are offset, so you'll start turning when you take it out of gear.

Hippocampus · Jun 16, 2022

Good post CJ but would opine many don’t go to singles for reasons of fuel consumption. I know that wasn’t in my calculus. As regards running aground in skinny water or hitting detritus having some protection to the running gear, especially prop, was.
HAve gone through the windless saragasso sea multiple times. In recent years the saragasso weed as gotten so extensive bulldozers are used to clear it off the resort beaches. It’s so bad you can’t hope to fish as lures clog nearly immediately. When passing through you periodically stop then back down in an attempt to clear weed. Both the ditch, the Delaware and the C & D periodically are inundated with detritus. Mostly branches and other vegetation. Some fairly large and floating just below the surface. Don’t like exposed running gear. Haven’t hit a container yet. But did dodge a new car with the white plastic on its hood and roof as well as a refrigerator. So think as with everything concerning boating “it depends”. There’s no perfect boat nor engine decision. If there was that would be the industry standard. You trade one risk or downside for another with any boat decision. You can only choose what may make the best sense for your type of boating.

mvweebles · Jun 16, 2022

catalinajack said:
Peter, those DriveSavers are gone. If I ever acquired a boat that had them, they would be the first improvement (removal) I would make. In my post I did not mention how one of them failed. I gently ran aground on sand at Cayo Costa in Florida, a story in itelf. It should have been a simple matter of backing off the sandbar and it started off that way. The boat began to move and I applied more throttle to get her free. But, the plastic coupling ripped apart leaving me with just one engine. It was the morning of Christmas Eve day. The tow boat showed up to pull us off three hours later. No way he could have pulled our 56,000# boat 45 miles to port. We would have been stuck there for at least two days waiting for a more powerful tow boat. So, yeah, having another engine saved the day. We pulled into the Legacy Harbor Marina in Fort Myers in the dark.

Yes, a failed engine of two will hobble but a failed single stops one dead, IN PLACE. I fail to see your point on this one.

As far as the annual maintenance, implicit in my response was that the maintenance is done by the owner which is the case for many of us. Valve adjustments, engine alignments, idle adjustments are clearly not annual maintenance items. Sea strainers? Annually? How about maybe weekly. Belts? Maybe every three years at a cost of $15 each. I'll grant you the heat exchangers should be cleaned every couple of years. So, yes, if paying a technician, the cost is easily $1K. Doing the work yourself, the cost is pretty much insignificant. I should have made that distinction.

As for the distance cruising assertion, I wasn't distance cruising when that DriveSaver blew. But having that second engine got me to port safely where I could deal with the repair at my leisure. I would not ever choose to cruise on one engine but a lot of boaters do that regularly to save a bit of fuel. I couldn't be bothered but it is fairly easily done especially with Velvet Drive transmissions

The DeFever engine room, yes, it is not stand-up at just 5'5" tall but I can assure you it is of no consequence even to this 6'1" guy. Not much of the work there is done standing up. The DF44 is not the only boat with twins having good engine room access; to wit, some Marine Traders; Great Harbours, there may be others but the DeFevers are not unique in this regard. Now, Bayliners, Grand Banks 42s, not so much.

Twins rarely as well maintained as singles - please. As a member of the DeFever owners association I can assure you that DeFever owners are just as meticulous about maintenance as any single owner. And, I think this is true among most owners quite the opposite of rarely as you opine.

The reason I say twins are frequently not as well-maintained as a single is due to outboard access. Not saying it has to be that way, but it very frequently is. It's the reason I like the DF44 engine room (and although I'm 6-foot, consider it to essentially a stand-up engine room due to mannerly door access vs hatches). Now, I'll go one further and say its not necessarily true that single-owners maintain their engines to top standards, but it's easier, less expensive, and there's the 'all-eggs-in-one-basket' motivation. Sailors converting to trawlers very often specify twins not for speed, but for redundancy to which I observe "If I maintained and operated my engine like many sailors do, I'd want a spare engine too!"

Thanks for the info on DriveSavers. I've seen them but never really thought much about them.

I think BandB summed it up pretty well. It's a really personal choice, and (my commentary not his) once made, tends to have confirmation bias on why your choice is a good one and transferrable to a rule. I can tell you the reasons I like a single stem primarily from I like displacement speeds and want a boat designed for them, running-gear protection and ease-of-maintenance (I'm not a great mechanic and need all the benefits I can find). Circling back to the OP and costs, that is way down the list, though these days when I think of burning 200-gals and coughing-up $1k or more, it would enter my mind, but maintenance costs would not just because as you say, I do my own work and working on two side-by-side engines is not enough of an additional cost/effort compared to a single (except for the outboard-access issue).

Peter

Marco Flamingo · Jun 16, 2022

Interesting that having twins in a grounding situation can be seen as a benefit. As the boat heels, one prop/shaft is damaged, but the other one is saved. Yeah! Same with having the props exposed to logs and submerged pilings. The other prop might not be damaged as bad. That allows the boat to limp home on one engine, allegedly a benefit.

Darn it, I only have a single engine, so when the tide came back in I simply motored away. I heard a log bump along underneath me last week, but it couldn't get to my single prop. But now that I know twins are "safer," I'll try to be paranoid.

I think the safety argument is a wash at best. The maneuverability claims have some merit, with the understanding that the skill of the captain matters more. A lot more. It is still possible to ram the dock with twins, bow thruster, and stern thruster. I've seen it done.

Operating Cost of Single versus Twins

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