Okay, single or twin??

Ski in NC said:

One thing I notice is noise quality. With twins there is always a bit of a beat frequency from the engines being even slightly off sync. Just a pet peeve of mine, a truly minor issue.

Also, mine being a single, I know the engine must be as reliable as possible. So it gets first rate maintenance, issues are handled right away, wiring is first rate, a good set of spares and tools carried.

I sea trial boats as part of my business and many twins are treated differently: "Hey I've got two, if one poops, I can still get in.." Neither particularly well maintained. Well if one poops, it still is going to screw up your trip!!

I'm not discounting the advantages of twins, those are real.

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You don't happen to be a pilot so you! I once had a discussion with a pilot/boater. He said that out of sync twins were his biggest peeve since flying jets he was attuned to well synced engines and was trained/experienced to tune consistently!

The one comparison that kinda sticks out is how many single engine planes are flying.

They are just maintained correctly.

semi-planing said:

Ask the question of the crew of the El Faro when you get a chance...

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If you could talk to the captain, I suspect he would report that it is bad luck to work on the engines / propulsion during a hurricane...

Ski in NC said:

One thing I notice is noise quality. With twins there is always a bit of a beat frequency from the engines being even slightly off sync. Just a pet peeve of mine, a truly minor issue.

Also, mine being a single, I know the engine must be as reliable as possible. So it gets first rate maintenance, issues are handled right away, wiring is first rate, a good set of spares and tools carried.

I sea trial boats as part of my business and many twins are treated differently: "Hey I've got two, if one poops, I can still get in.." Neither particularly well maintained. Well if one poops, it still is going to screw up your trip!!

I'm not discounting the advantages of twins, those are real.

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Get an engine sync and you won't have the drone of slight variations of twins.

Nothing is foolproof to a sufficiently talented fool.

Several factors come into play in the decision process:

Fear or break down can certainly be resolved by vessel assist if their available in your area, as is the case for probably 90% of TF members. If you plan to cruise in extremely remote areas, one can make a case for twins. However a number of our members travel to extremely remote areas including crossing the Atlantic with a single.

Are or will you be an infrequent boater as most on this forum. Proficiency in general comes from frequent repetition. If you consider that well over 90% of commercial fishing boats under 60' are singles, then it's easy to see that maneuverability is a limitation of the operator in most cases and not the vessel. With the exception of the need for more HP than a single can provide, in many cases, twins are a crutch for lack of docking proficiency. Adding a bow and even a stern thruster to a twin is the second crutch. Don't agree with this? How many sailboats under 60' have you seen docking with twins?

How do you feel about engine maintenance? While not a hard and fast rule we see far more breakdowns of one engine in a twin engine boat than single engine boat breakdowns. There are a lot of boaters that view twins as redundancy and consequently do very little maintenance assuming that when one breaks the other will get them home. This doesn't apply to everyone with twins, but I would wager it was the majority in recreational boating. In general, single engine boaters tend to be more preventive maintenance oriented for the obvious reason. Yes there are those that don't do PM regardless of how many engines they have.

One can debate whether a single protected screw makes more sense than twins when running aground. I would argue that learning to navigate and avoiding shoal waters is a far better choice.

So to my mind, the choice of single versus twins is really more based on what type of owner operator you will be. If you will be an infrequent user, not big on PM, and have a phobia regarding engine failure, twins would be a logical choice.

For the incredible complexity and unreliability of the modern engine, wonder how many twin advocates on this forum wouldn't have a single engine car.

Ted

I believe that a neglectful owner will be neglectful and a meticulous one will be meticulous single screw or twin, so I don't really buy into the "twins are less maintained" argument.

If the OP's cruising area has towing service available, I think a single will be fine. If there's no towing service, I would opt for twins or a single with a get-home set-up. Peace of mind is very important to me.

If there were a "get-home genie" going around offering free get home engines to single screw boaters, I'm sure most, if not all will take the free offer. Even those that claim to not believe in the value of redundancy.

"One can debate whether a single protected screw makes more sense than twins when running aground. I would argue that learning to navigate and avoiding shoal waters is a far better choice."

Great where the Hooligan Navy is there to set buoys for you , but the reality is if you go cruising you WILL run aground eventually.

Trees ,trash in the water and thin water play havoc on exposed shafts , props and rudders, never mind the occasional sea land container.

There probably is no "best" so the concept of purchase the interior you like and deck house style that you think is attractive probably does work as well as dithering.

The best advice is probably to purchase a boat that is currently doing just what you want to do, and save months and thousands in "conversion" or "upgrading".

A cruiser is outfitted as a cruiser a cottage as a cottage .

O C Diver said:

So to my mind, the choice of single versus twins is really more based on what type of owner operator you will be. If you will be an infrequent user, not big on PM, and have a phobia regarding engine failure, twins would be a logical choice
Ted

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Speaking of phobias, I heard about a guy who was so OC about the singles vs twins discussion on TF that he removed two perfectly good engines and put in one

When I look at the working boats in this area all I can say is that they are 100% singles. These are boats that are out on the water 10-12 hours a day 6 days a week. I am talking about lobster boats generally in the 35 to 50 foot range with most 35-45 feet. They don't seem to have much trouble with engine failures. Sure they do happen and they very occasionally result in the loss of the boat (largely because lobster boats often work close, as in 10-20 feet, from ledges and rocks, where a blown transmission results in the boat being on the rocks in seconds). Reliability of a properly maintained diesel really isn't much of an issue. Incidentally, there is no towing or vessel assist around here. We also have 12-15 foot tides locally and up to 25 foot tides a few miles further down east with the associated currents. On top of that if you go more than three miles from the harbor you are in the open ocean where things can get nasty fast.

As far as maneuverability is concerned, I think what you are really talking about is ease of maneuvering. If you know your boat and have significant experience with it, maneuvering isn't a problem. I see lobster boats come into tight spaces all the time without any trouble. That is a boat that is often single handed, with a single engine and no bow thruster.

I have always had singles and really don't feel the need for twins for any of the reasons noted above. Maintain your engine properly and know your boat and you won't have any problems with a single.

Jimbo2015 said:

The one comparison that kinda sticks out is how many single engine planes are flying.

They are just maintained correctly.

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There are more planes in the water than there are boats in the air.

One rarely mentioned bonus with twins: When you have a breakdown that requires a trip to the mechanic, you can schedule that trip for a time that you are not using the boat, rather than losing your vacation time or spoiling a trip you have just begun. The only differences; you will be running a little slower, as you now have only 1.2 the hp, and you will need to re-acquaint yourself with the handling of the boat under a side mounted single.

There's a current engine failure thread on the board wherein three separate owners of singles mention power loss...not including the El Faro. A recent thread spoke of a prop fouling on a twin. Power related malfunctions happen with great regularity to unsuspecting owners who are seemingly very fastidious about maintenance. Happened to me because of a raw water pump that had been rebuilt incorrectly by a very reputable company. Check the archives....there are documented incidents all over the place...many of them in less than ideal circumstances. The tow boat argument doesn't hold water in many (most?) cases.

koliver said:

One rarely mentioned bonus with twins: When you have a breakdown that requires a trip to the mechanic, you can schedule that trip for a time that you are not using the boat, rather than losing your vacation time or spoiling a trip you have just begun. The only differences; you will be running a little slower, as you now have only 1.2 the hp, and you will need to re-acquaint yourself with the handling of the boat under a side mounted single.

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And another bonus: With two engines you have about twice the probability of this happening.

And I seriously doubt someone is going to continue a journey with one dead engine. There are sea conditions that can make that a very tough situation.

Ski in NC said:

And another bonus: With two engines you have about twice the probability of this happening.

And I seriously doubt someone is going to continue a journey with one dead engine. There are sea conditions that can make that a very tough situation.

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Advocating single engine airliners?

Ski
I mentioned this because




"Ski: And I seriously doubt someone is going to continue a journey with one dead engine. There are sea conditions that can make that a very tough situation."

I mentioned this because it happened to me. My engine failure occurred in June. I scheduled the repair for mid Sept, which allowed the yard to schedule parts and mechanic time well in advance and allowed me to continue my summer trips unimpeded by out of service time. Of course, sea conditions in the protected waters of the BC inside coast were not a factor.

Bay Pelican said:

The redundancy factor is not very important as most diesel shutdowns are fuel related and will shut down both engines.

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In our experience and observation this is something of a myth. I do not know or know of anyone, power or sail, in our area who has had an engine shutdown due to fuel. We have had five engine shutdowns-- we shut the engine down-- in the 17 years we've had our boat. None of them had anything to do with fuel except one when I let an engine get a slug of air during a fuel transfer.

Our other precautionary shutdowns have all been cooling related. As were almost all of the other engine shutdowns I know about, power and sail. I also know of a precautionary shutdown due to an injection pipe pinholing and a couple due to transmission problems. And I know of some due to running gear damage from hitting or getting tangled up in debris. But shutdowns due to bad fuel or other fuel-related problems (other than running an engine out of it)-- not one.

Now maybe in areas where fuel quality is an iffy proposition fuel-related shutdowns are a more common problem. But in this region where fuel seems to be good just about everywhere I have never even heard discussions about fuel issues on the dock or in our club. It's certainly not anything we give any thought to.

Now if a boat has filthy fuel tanks with years of accumulated crud in the tanks then fuel starvation due to filter clogging could certainly be a potential problem. But even that is unlikely to shut down both engines of a twin unless the boat has a poorly designed fuel system.

So in our experience and observation the likelihood of both engines in a twin being shut down because of a fuel problem, or any other problem frankly, are slim to none.

A few years ago I met a boater who had one of his transmissions (nope not fuel related) fail on his twin GB. This was in Wrangell and he was from Tacoma. So he carried on to Juneau, Glacier Bay and eventually back to Tacoma all on one engine.

Ski in NC said:

And I seriously doubt someone is going to continue a journey with one dead engine. There are sea conditions that can make that a very tough situation.

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Not true at all. I know several people, including ourselves, who have continued a trip on one engine after a precautionary engine shutdown. Some of these trips have been pretty long-- several hundred miles back down the Inside Passage in some cases, sometimes in snotty weather.

As to the notion that having two engines doubles the risk of an engine shutdown, while statistically that's true I think reality makes that pretty much an armchair theory. The picture it paints of the owners of twin engine boats suffering engine shutdowns on a regular basis is rubbish in my opinion. Most of the owners of twins that we know have never experienced an engine shutdown (yet). We have, although none of them were related to an engine itself. And the things that caused us to shut one of our engines down would have caused us to shut our one engine down had the boat been a single.

But the one "statistic" that is as true in reality as it is in theory is that if you have to shut an engine down in a twin you can continue on the other engine, where if you have to shut the engine down for exactly the same reason in a single you will continue on the end of a rope. Unless, of course, you have the parts, tools, and skills to repair the problem and get the engine going again.

And in this area, anyway, while you are mucking about trying to get that one engine going again the currents will be having a grand time carting your boat to wherever they feel like carting it including the rocks of which there are quite a few up here.

In 15 years with the same boat had one oil pressure sensor fail, one water hose started to leak and spray around in both cases I just shut down the one engine and continued on to my destination. I could have anchored and dealt with it as well. There were well maintained engines but stuff does happen and because I had twins it was a non stress situation.


Most twins I have seen have two tanks that can be used independently. My ZF trans didn't care about lazy engine operation. The maker told me to check the temps and switch side every two hours. He also reminded me that boats get towed and props spin at docks in current without problems just don't try to go too fast.


Prop protection is a nice feature of singles but it would not have benefitted me over those years.


The dockside maneuverability cant be beat.

The furthest I have gone on one engine is about 180 miles. Had to beat weather and currents so after shutting down that side it took about 4 days to figure out the problem and solution. It was an after cooler failure so quite simply bypassed it - thanks to NAPA Ketchikan for necessary hoses and fittings - started up and carried on for another 500+ miles.

The rudder offset was about 6 degrees and speed dropped to around 6.5 knots from a normal 8.2. Engine temperatures increased by 10 degrees to around 183F due to now being over propped on that one side. EGTs crept up from a normal 500 to about 650 F. Trailing prop shaft and transmission temperatures steadied out at 120F, only slightly higher than if engine were running.

All in all it was a great learning experience. I had the Engineer from a large yacht help me trouble shoot and he was as initially as befuddled as I was regarding problem/solution. Ultimately the issue was traced to leaks in the after cooler soldering joints due to using a non compatible barnacle removing product. This product was used by a very experienced yard and lead mechanic who has since left the firm.

Phyrcooler said:

Walt - curious if your singles had thrusters?

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Both my singles had bow thrusters. (I wouldn't have it any other way!) One was a Mainship Pilot 30 & the other was a Halvorsen Gourmet cruiser 32. My biggest reason for wanting twins is for more speed. Redundancy had nothing to do with my decision.

Years ago when I was earning my multi engine rating, my instructor (an old Navy pilot) told me that wanting a multi engine airplane because it's safer is BS. They require more maintenance, cost more, more skill and knowledge is required and in planes of that day (1967) when you lose and engine, you get to pick your crash site. (I know this was exaggerating but it did hit home.)

Nope, If I could have bought a single engine boat with speed in the high teens & everything I now have in my OA, I would have done it! Singles with bow thrusters and a Tow Boat US membership are great! (Most of them are too slow, however.)
1) Mainship Pilot 30
2) Halvorsen 32 Gourmet cruiser
3) Ocean Alexander 42 Altus

I think it is very important for all boats to have more than one means of propulsion. Twin engines satisfies this best. An inflatable dingy with a larger outboard lashed to the hip might do. An outboard motor on a swimstep motor bracket might work for some boats. Small motor boats can use oars. Row boats that loose an oar can be paddled with the remaining oar. A kayak can be moved using hands as paddles.

Sails are a nice choice. Not very useful with no wind. However, emergency situations with no wind tend to be not so much of an emergency.

Steve

We've had two situations where one engine had to be shut down and we had to go home on one engine. Coincidentally, both happened while we were in or entering the lock at Ice Harbor Dam, and both happened to the stbd engine.


On the first, an o-ring in our hydraulic steering failed and left that engine stuck in reverse. I shut down the engine and we were able to get into the lock and secured on one engine. We then had to get home on that single engine.


On the second, we were tied up in the lock and had a runaway starter motor on the stbd engine. I shut off the batteries for that engine and we came home on one engine.


In both of those situations we'd have been totally screwed if we had only one engine because there's no Sea Tow around here and the USCG won't tow except to prevent loss of life or environmental damage.


I did notice something interesting on the trip home after this last incident. Normally, to cruise around 10-10.5 kts on two engines the tachs are around 1050-1100 (depending on load). When running on just the port engine, to maintain that speed I only had to up the engine rpm to 1250. It required some hard rudder to port to maintain a straight ahead course, but only 150 rpm's more power.


I've owned boats with singles and twins. Never again will I buy a boat above 25' with a single engine.

Panope said:

Sails are a nice choice. Not very useful with no wind. However, emergency situations with no wind tend to be not so much of an emergency.

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Steve, I see that exactly the opposite. An engine failure with no wind IS an emergency for me.

In our joint waters, currents will mess you up in a hurry is you lose power in the wrong spot at the wrong time. Because of that, I don't view my sails as a backup to my engine. In a narrow channel or coming into a dock if I lose my engine my sails will not help me, wind or no.

Even so, as I look to moving to a trawler, I see twins as more of a negative than a positive. Like most of us, my opinions are based on my own experience. As a kid, sailing my parents 21-29 foot sailboats with outboard gas engines, suffering an engine failure was all too common. However I have only had one time when I needed to shut down a Diesel engine on a sailboat and that was an overheating issue and I shut the engine down preventively but could have kept it running for a while if we had been in immediate peril. Maybe my small Yanmar is more reliable than the larger engines found in a trawler?

Having said that, the ideal setup is in the GH37 that has two of the 56hp Yanmars that I have in my sailboat. Economical, reliable, easy to maintain, maneuverable and redundancy.

sunchaser said:

Speaking of phobias, I heard about a guy who was so OC about the singles vs twins discussion on TF that he removed two perfectly good engines and put in one

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Who was that? I had one and replaced it with one.

Ted

AusCan wrote:

Advantages (in order of importance)

Twins
- Better manoeuvrability
- Redundancy

Single Engine
- Protected prop & rudder
- Better accessibility
- Lower costs

AusCan summed it up neatly. I've operated and maintained twins and singles of various types. To me, a single is preferable for exactly the reasons he lists. As for a bow thruster, in my younger days I used to sniff indignantly at the idea, but lately not so much.

mahal said:

I believe that a neglectful owner will be neglectful and a meticulous one will be meticulous single screw or twin, so I don't really buy into the "twins are less maintained" argument.

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You missed the obvious point. A person who recognizes they are not maintenance focused, may pick twins for redundancy. This has nothing to do with whether a twin engine owner is meticulous. It is a very common occurrence to see boaters with twins who know they have a problem continue to use the boat weekend after weekend because they know they have a second drive train to come home on. The guy next to me had a velvet drive going bad and kept doing canyon fishing trips until it quit. He was hoping to get the last of the season in before pulling the gear. Never let PM get in the way of going fishing.

Ted

Here are my thoughts

As others have said - people will tend to recommend what they have. That's not just because they don't want to admit they're wrong, but also because they may well have put quite a bit of thought into it before they made their purchase.

I think former sailors are more inclined to buy a single engine boat. I'm in that category. Contrary to popular belief a sail isn't much of a backup means of power if you are close to danger. It's more useful on a longer passage.

While twin engines may be easier to maneuver, you shouldn't shy away from a single. My bowthruster is intermittent right now so I'm getting good practice maneuvering my 80,000lb boat without them. Lots of people do this all the time.

If you're going to be continually apprehensive about having a single then get twins. Feeling a sense of confidence (not complacency) is a good thing - if twin engines are what it takes then you should get them.

I bought my boat because I really wanted it! I would have still wanted it had it had twin engines. I am considering adding a hydraulic get home motor driven from my 20kW generator one day. I will probably add one before an ocean crossing, if I ever do one.

I hope the OP is enjoying all the comments!

Richard

O C Diver said:

You missed the obvious point. A person who recognizes they are not maintenance focused, may pick twins for redundancy. This has nothing to do with whether a twin engine owner is meticulous. It is a very common occurrence to see boaters with twins who know they have a problem continue to use the boat weekend after weekend because they know they have a second drive train to come home on. The guy next to me had a velvet drive going bad and kept doing canyon fishing trips until it quit. He was hoping to get the last of the season in before pulling the gear. Never let PM get in the way of going fishing.

Ted

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"You missed the obvious point." I doubt it. I was responding to an earlier poster that said single screws get first rate maintenance, implying that twins don't. "A person who recognizes they are not maintenance focused, may pick twins for redundancy." What a ridiculous thing to say. Have you really met or heard of someone that picked a twin screw because they're not maintenance focused?
Regarding your neighbor, what he did is not exclusive to twin operators. Just talk to tow boat captains and you'll be amazed at what single screw owners are up to. They are almost 100% of their clientele.

mahal said:

"You missed the obvious point." I doubt it. I was responding to an earlier poster that said single screws get first rate maintenance, implying that twins don't. "A person who recognizes they are not maintenance focused, may pick twins for redundancy." What a ridiculous thing to say. Have you really met or heard of someone that picked a twin screw because they're not maintenance focused?
Regarding your neighbor, what he did is not exclusive to twin operators. Just talk to tow boat captains and you'll be amazed at what single screw owners are up to. They are almost 100% of their clientele.

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You did miss the obvious point. I was the one that stated my single gets first rate maintenance. And the reason for that is I know I count on that engine exclusively. If I had twins I would not be so anal. That is the point.