Twins? Should I be intimidated by twin engines?

[BruceK]

Should I be intimidated by twin engines

As I shop for a boat....What are the pros and cons of twin engines? Would you recommend twins, and why?
Thanks.

You are more likely to be intimidated by the replies than the twin engines.
While there are some great single engine boat handlers, most will get better control from twins. Especially maneuvering at close quarters, like docking, and threading your way through a mooring field. The trade off is running and maintaining two instead of one. Having had one and now two, doubt I`d go back.

 

[bikeandboat]

Had several twins. Finally went single. Will not go back.

 

[BruceK]

You see what I mean, Acheron 2010? For everyone with one view there is someone with the reverse view. Best of luck. Maybe look at the reasons people give for their view.

 

[Tom.B]

Had several twins. Finally went single. Will not go back.

So are we still talking about boats here, or are you a former actor in adult films?

 

[Peter B]

Here's my take on it. I have a planing hull with twin Cummins eng's. While I can go fast with it (saw 23 kts on GPS at WOT) I don't plan to use it like that very often. Most of my travel will be cruising at 7 or 8 knots and I won't need both engines to get to where I want to go so will be running on one engine to get there, the other to get back but have the option to use both when I want. Hopefully the new autopilot (still in the box soon to be installed) won't have any problem keeping the boat on course with the boat wanting to pull to one side. Maneuvering in tight quarters way easier with twins (unless you have a bow thruster).

Not wishing to throw a dampener on your plan, but how will you address the issue, when running on only one engine at a time, especially when it will be by choice and often by the sound of it, of preventing over-heating of the gearbox of the free-wheeling prop, and possibly the overheating of the presumed dripless shaft seal..? Have you already set up a simply and quickly deployed prop-shaft clamping system on each, and a cross-fed water-flow to the shaft seal, or are your engines set up to allow one at a time use without any special tactics needed..? Just curious, because those issues are usually brought up as something that makes just running on one engine at a time to save wear and fuel just not worth it overall.

 

[O C Diver]

Here's a radical thought, if you have narrowed down your search to a make model and size, see if you can rent one or both to see how they handle and level of complexity.

To me for near coastal or inland cruising, one engine would be my recommendation up to about 50'. For cruising to remoter areas like the Bahamas or much of Alaska, twins offer a nice redundancy. I would consider twins on boats above 36'. Below 45' on some boats and below 36' on almost all boats, twins turn the engine room into a sardine can. Working on the hull side of twins in small boats can be a nightmare. Also, on smaller boats the added weigh of the second drive train can force compromises in fuel and water tank sizes.

Ted

 

[Andy G]

Not wishing to throw a dampener on your plan, but how will you address the issue, when running on only one engine at a time, especially when it will be by choice and often by the sound of it, of preventing over-heating of the gearbox of the free-wheeling prop, and possibly the overheating of the presumed dripless shaft seal..? Have you already set up a simply and quickly deployed prop-shaft clamping system on each, and a cross-fed water-flow to the shaft seal, or are your engines set up to allow one at a time use without any special tactics needed..? Just curious, because those issues are usually brought up as something that makes just running on one engine at a time to save wear and fuel just not worth it overall.

Danger, danger Will Robertson, major hijack alert. Man the pumps.

 

[Peter B]

Danger, danger Will Robertson, major hijack alert. Man the pumps.

Naughty Andy. It's not a hijack at all, but an absolutely relevant subject to raise in this single versus twin thing, when folk refer to it as their safety net, or get home engine, or talk of using only one as an everyday option.

 

[RT Firefly]

Greetings,
I fear we may have scared Mr. 2010 away unless, he is in fact at this moment poring over the archives. Allow ME to be the first to apologize...

 

[Ken E.]

Not wishing to throw a dampener on your plan, but how will you address the issue, when running on only one engine at a time, especially when it will be by choice and often by the sound of it, of preventing over-heating of the gearbox of the free-wheeling prop, and possibly the overheating of the presumed dripless shaft seal..? Have you already set up a simply and quickly deployed prop-shaft clamping system on each, and a cross-fed water-flow to the shaft seal, or are your engines set up to allow one at a time use without any special tactics needed..? Just curious, because those issues are usually brought up as something that makes just running on one engine at a time to save wear and fuel just not worth it overall.

Pete, not trying to speak for Nightsky, but I have twins and travel on one engine on the longer legs to Alaska and back, a few thousand miles each summer. Your points are valid. First, on the dead engine, the gear must be rated for free-wheeling or the shaft locked down. Most but not all Twin Disc gears can be free wheeled and the owners' manual give the models as does the TD website. You are also correct on dripless shaft seals; each seal must have water supplied from both engines, thereby ensuring cooling when one engine is offline. My fuel savings is about 20%, running on one side to achieve 7+ kts hull speed.

 

[djones44]

Twice the weight twice the fuel twice the service cost twice the repairs twice the noise twice the shaft seals twice the gearboxes twice the props twice the rudders 1/2 the area to work on and they get you to the same destination as a single at 8 knots

Also, two engines may actually involve a third engine (generator) and one or sometimes two thrusters. In an older boat the maintenance effort and the inherent costs looming in all that machinery - you better be a mechanic or wannabee or the experiment will end itself, abruptly.

I downsized to a single, upgraded to an autopilot, and kept the generator and stern thruster. At 34' it's all there's room for, and I couldn't see running 3 diesels as advisable in an older, modest boat.

I'd love a Beneteau 34 with a single 375HP and 20Kn, its generator a get-home, now that's a sumptuous design that makes sense to me.

 

[Irish Rambler]

How often does a well maintained single break down ?
Ken E mentioned Scotch whiskey earlier in the thread.
May I respectfully point out that the Scotch drink is spelt Whisky and is only distilled twice.
The Irish drink is called Whiskey, spelt with an E and is triple distilled for purity.
Buy some, we need the exports.
Bushmills Whiskey distillery in the North of Ireland is the oldest registered distillery.
Powers, Jamiesons and Paddy are long established distilleries.
The Italian Guigliano Marconi ( who invented the radio) married into an Irish whiskey distilling family.
Just a bit of useless information to keep the pot boiling.

 

[Peter B]

How often does a well maintained single break down ?
Ken E mentioned Scotch whiskey earlier in the thread.
May I respectfully point out that the Scotch drink is spelt Whisky and is only distilled twice.
The Irish drink is called Whiskey, spelt with an E and is triple distilled for purity.
Buy some, we need the exports.
Bushmills Whiskey distillery in the North of Ireland is the oldest registered distillery.
Powers, Jamiesons and Paddy are long established distilleries.
The Italian Guigliano Marconi ( who invented the radio) married into an Irish whiskey distilling family.
Just a bit of useless information to keep the pot boiling.

Washall that godda do wish shinglesh vershush twinsh..hick..!

 

[North Baltic sea]

But you can go MORE than twice as fast as a single if ONE engine fails.

I only have one engine.

sometimes this way, sometimes it does not. The boats are so different to run, due to hull design and power of the machine or machines.

there are some SD hull with two big powerful machine to run right to force teenagers and this is reflected by realy high consumption and a large stern wave...

 

[FF]

To me twins are great for the speedboat that has enough fuel to get where he wants to go , at speed.

The hassle I see , esp for the inshore displacement cruiser is prop damage.

Trash abounds in the waterway , and an accidental grounding does happen, and the Maineiacs do string their lobster pots from channel buoy to buoy..

A centerline single screw reduces the dangers.

In many boats the room to maintain the engine is far superior for the single.

 

[Lou_tribal]

I would concentrate on finding the boat you like that will meet your needs, then go with whichever it happens to have, single or twins. Each have their advantages and disadvantages.

Like he wrote... find the boat you like, and more important ensure engine(s) is(are) in good shape well maintained and running fine.

On a personal side, I have a single and for my usage it is fine, I never tried twins yet so cannot argue.

L.

 

[ranger58sb]

I suggest you do a search using the search function, because as others have alluded to it, there has already been MUCH discussion on here re this very subject.

Yep. FWIW, I'm firmly in both camps. I'm more interested in features and performance than I am in engine count.

Oh crap.
Sorry. I'll go right over to a gun forum and ask 9mm versus .45, ok?

Did not mean a Hatfield-McCoy thing. I've been taught handling skills on a single prop, so just don't know the difference.

Heh... you picked that up fast!

Your single skills will benefit twin handling. You won't be intimidated; easy transition.

But I still recommend you find the boat that suits your needs/wants without regard to how many engines it may have. You can evaluate that part of it after you find good candidate boats.

-Chris

 

[BandB]

The hassle I see , esp for the inshore displacement cruiser is prop damage.

Trash abounds in the waterway , and an accidental grounding does happen, and the Maineiacs do string their lobster pots from channel buoy to buoy..

A centerline single screw reduces the dangers.

We've all heard that said many times, but that doesn't necessarily make it so. Sometimes conventional wisdom, is just convention and not necessarily wise. I contend this is more on a boat by boat basis.

Some twins have very good and protective prop tunnels. Others have some keel protection. Meanwhile, given the exact same boat, the draft of the single is often greater because the prop is at the deepest point of the boat. So, sometimes while the single might even be less likely to suffer damage if run aground, it's more likely to run aground. Plus there is always the chance with twins you only damage one prop and still have one in good condition and on singles, it's the only prop. Of course, if both props, then twice as expensive to replace.

 

[Seevee]

The Twins vs Single argument never ends.....

Comparing the SAME boat.......

What you get with twins:
A very slight increase in operating costs (fuel burn for single at twins at best economy speed can be almost identical)
More maneuverability
More speed (at a price)
Double the chance of engine failure
Less room in the engine compartment
And a bit more maintenance to do

With a single you get:
More simplicity
Only one chance for engine failure
Better room in the engine compartment
Less maneuverability, but with bow and stern thruster, may not be a huge deal

There's no difference with intimidation... in fact a larger boat may be more intimidating with a single.

====
Today, I like twins

 

[bayview]

I have had more singles than twins. Overall I prefer twins if the boat is big enough. Many twins are completely independent systems so there is true redundancy. With twins the boat can virtually dance around the docks. That isnt really necessary but a boat isnt really necessary either.

 

[smitty477]

Curious how many folks have really owned and/or spent large amounts of time with both a twin and single engine?
We have had many seasons with each type and absolutely say that they each have their uses and strengths - would not switch out one for the other unless the goals at the time had changed.

 

[RT Firefly]

Greetings,
Mr. 477. Started with twins in first boat (34') larger than a skiff. 12 years. Went to a single (34'). 13 years. Now have twins (45'+). 10 years so far. I agree with your conclusion. Oh, also have single 23' Penn Yan. NOT an IO, a full inboard.

 

[BandB]

Curious how many folks have really owned and/or spent large amounts of time with both a twin and single engine?
We have had many seasons with each type and absolutely say that they each have their uses and strengths - would not switch out one for the other unless the goals at the time had changed.

I have and haven't. I had experience with single engine bowriders 25' and under, but all my experience with larger boats has been with twins. I do have a basic understanding and while my choice is twins, I do not argue that they are the only way to go and readily admit that for many single engines are an excellent choice.

 

[O C Diver]

One of the points that's often missed in this discussion is the rudder (s). Having operated several of each, steering can be quite different. If the OP is primarily experienced with single engine boats, he is probably used to a much more responsive rudder. Singles require this to have reasonable docking ability. While not all twins have much smaller rudders than the same make and model with a single, most twins will. While dock a twin by jockeying the two engines between forward and reverse makes docking quite easy, the failure of one engine can make close quarters maneuvering and docking near impossible. While this isn't a reason to avoid twins, one should spend time during seatrial to see how well it handles with one engine disabled. If you're buying twins for redundancy and navigate narrow channels such as the AICW, it's important to be aware of your vessels reduced mobility on one engine.

Ted

 

[North Baltic sea]

And what say engine Experts!


Single Or Twin Engines- Which Is Best? | | PassageMaker


Grounds for twins is hypothetical fears or neglect routine maintenance and inspections. If the fuel is cheap as US is of course less interest in fuel cost, double or maintenance costs.

 

[Nomad Willy]

Still the biggest difference between singles and twins is weight and power.

Should'nt be that way but most of the old trawlers employed only the 6cyl Ford Lehman engine. The GB 36 (as example) should have had a 180hp (about) engine as that amount of power propels the boat at the speeds it was designed for. 12 or more knots is overpowered and 7 or less is underpowered. Just an example and the numbers may be slightly wrong but it's about right.

So a single should be a 180hp engine and twins should be two 90hp engines re the approximate example above.

If one wanted a single and a 12 knot cruising speed it should have a 300 to 350hp engine offered as a single or as a twin .. two 170hp engines. Generally speaking the number of engines should have nothing to do w the amount of power. A boat should have the right amount of power for it's design with however many engines customers want.

I've been critical of the GB before in this regard but it applies to many trawlers. Especially those made in the 70's. So one shopping for trawlers that offered the FL engine only the greatest difference between singles and twins is power, weight and cost. The fact that there is one or two engines is fly stuff.

 

[Britannia]

Not mine, but.....

How about full displacement with keel, skeg and rudder with
pintle bearing on the skeg?
Add twin engines, run either or both together.
The prop is between the deadwood and the rudder.( I have seen
pictures with shafts "in the open")
Think the draft is too much for the loop.

Ted

Single engine with keel, skeg hung rudder here. Like the protection for the running gear.

 

[BandB]

Our primary reason for twins is simple. Power and performance. It's not redundancy, it's not handling. Those are all additional reasons but they don't even come into play in our decision making because we've already chosen twins to have the power.

As to the article pointed out, it talks about "commercial boats" but it really speaks about a small part of the commercial boat population and it's not accurate. It states, "Did you know nearly one hundred percent of the commercial fishing and workboat vessels (of all sizes) are single screw/one engine boats? Scallop draggers, lobster boats, charter fishing boats, longliners, crabbers, seiners, whatever- these vessels are all powered by a single diesel engine."

The "of all sizes" is where it really falls apart. Most larger commercial boats are multiple engines. Charter fishing boats in most areas are primarily twins. We just had someone here go fishing out of Westport WA. Tons of charter fishing boats there and nearly all are twin diesels.

What about all the commercial boats in the Gulf serving the oil industry? They're not singles. Add to this that the vast majority of boats of all types in excess of 60' are twins or more. Yachts? SF's? Only a few trawlers are not but they are the minority, not the majority of boats.

When an article leads with a basic falsehood, then it hurts it's entire credibility.

The information in the article is mostly correct when you turn the discussion to trawlers 60' and under which is relevant to this forum. However, the statements made early are blatantly misleading and the article is clearly written to express one view, not to give a broader view. It is a conclusion reached, now lets prove it sort of article. I would be just as guilty if I listed all the reasons to have twins including redundancy and handling and went on to state why twins were the only way to go when the reality is we choose twins for the power and for all the other arguments there are valid contrary arguments.

 

[FlyWright]

No matter which you pick, you'll eventually wish you had the other when:

with a single, your engine fails

or

with a twin, you foul your running gear on an underwater obstruction.

To me, the perfect world would be twins with full prop protection (bilge keels), but I suffer on through my boating life with a less-than-perfect boat. Woe is me...

 

[psneeld]

Smitty477....I have operated many of both types through various maritime jobs.