Do you prefer twin or single engine?

[stillwaters]

Just remember; God gave you two of everything important, not one:


Blimey,have you got two of those as well? I suppose it's useful for the three-in-a-bed weekends,though!

 

[rustybarge]

Certainly no need for them in a cat.
And use a SWATH cat and you could all but play snooker in a force 8

Slight thread drift, and slight size drift..........
I've got a shaft drive boat already, and now I've just got delivery of Motorcat hull; no not 25mtrs, but 25'.
Cut your cloth etc....

 

[Deleted User YDKXO]

Blimey,have you got two of those as well? I suppose it's useful for the three-in-a-bed weekends,though!

Yup, I've got twin shaft drive

 

[rustybarge]

Getting back to the OP's original question, a 55'-70' boat costs a hell of a lot to run in fuel, maintenance and mooring.
Imo it's a millionaires toy.....make that a multi-millionaire.

From another thread:

The only reason so many folks end up changing their first boat so quickly is probably due to them watching too many James Bond movies involving Sunseekers doing 30 knots in dazzling sunshine and with Pimms advertising dept picking up the fuel bill.
A far more realistic scenerio involves a stroppy wife and kids ,chilly east wind,a threat of rain and because the credit card card bill is due tomorrow,you will def not be calling in at the fuel berth and you will have to manage with whatever is in the tank.

 

[davids0865]

There is no right or wrong answer to this. Even the well known displacement trawler boat builders can't agree. Nordhavn tend to offer singles even upto 70ft or so and although they do offer twins, they try to encourage buyers not to specify them by reducing fuel capacity and fitting only a wet exhaust. On the other hand, Kadey Krogen seem to offer mostly twins, certainly in 50ft+ boats and Selene seem to hedge their bets, offering both on most models.
For me personally, there is no argument, it has to be twins. I've had too many instances of one engine going down and not just because a prop gets fouled and I would need a lot of persuading before I bought a boat with a single engine. Neither do I think that a wing engine is the answer. If you're going to pay for the installation and maintenance of a wing engine ie a second engine, why not just fit a twin engine installation in the first place? Not only that but wing engines tend to be ignored and not used which means they might fail when they're really needed. Neither do I accept that a single engine has to be more economical on fuel by definition. I once had a chat to Tony Fleming (of Fleming Yachts) at a boat show and he was adamant that a single engine is not always more economical than a twin as it depends on the choice of engines and the design of the hull
So, twins for me and if it costs me a bit more fuel and maintenance cost, I'm happy to pay that for the extra insurance

IMO the complete answer is a single engine plus a large genny with a pto to drive a hydraulic pump OR via a separate drive , the main shaft, this seems to be fairly common on "expedition" yachts.

 

[oceanfroggie]

Just remember; God gave you two of everything important, not one

Only one brain though

I'm a fan of both single and twin engine setups in the appropriate application.

 

[MapisM]

Similarly you wouldn't expect anything other than the same BS from boat owners with singles

Agreed in general, but as it happens I'm owning a TWIN engines trawler since the very beginning of this millennium (see avatar - the second prop ain't a reflection).
Still, it doesn't take a lot of my (single) brain to understand plain BS when I see/hear it.
Mind, I'm not saying that I know better than Tony Fleming - far from that.
I'm just saying that he was consciously lying, when he told you what he told.

 

[longjohnsilver]

Similarly you wouldn't expect anything other than the same BS from boat owners with singles Just remember; God gave you two of everything important, not one

What a lucky lady Mrs F is!!

 

[stillwaters]

IMO the complete answer is a single engine plus a large genny with a pto to drive a hydraulic pump OR via a separate drive , the main shaft, this seems to be fairly common on "expedition" yachts.

In order to drive a heavy displacement 55-70 footer at a realistic speed,taking into account that the get-you-home situation might be against a strongish current,it would need a power requirement of around 60hp minimum.That's quite a sizeable genny and much bigger than would usually be neccessary for other power requirements. Because of this,conventional wisdom seems to favour having a separate get-you-home engine either with a separate shaft/feathering prop or via a hydraulic drive to the main shaft,such as Keypower etc.
The perceived downside to reliance on one shaft only,however,is that if it is the cause of the problem rather than the engine then you really would be bu**ered.
Incidentally,Selene Yachts are quite prepared to supply a wide and ever growing range of sizes of displacement trawler yachts with either one or two engines but have no doubt that for long distance passage making,one slow revving lump such as a Lugger is far more economical than running two engines.

 

[LittleShip]

Stillwaters.....

one slow revving lump such as a Lugger is far more economical than running two engines.

Now I'm sure that a certain person who has posted on this thread will be along (as usual) to disagree with this statement.

Tom

 

[longjohnsilver]

Stillwaters.....

one slow revving lump such as a Lugger is far more economical than running two engines.

Now I'm sure that a certain person who has posted on this thread will be along (as usual) to disagree with this statement.

Tom

Tom, have you clicked on your own link recently??!!

 

[Philiz]

Stillwaters.....

one slow revving lump such as a Lugger is far more economical than running two engines.

Now I'm sure that a certain person who has posted on this thread will be along (as usual) to disagree with this statement.

Tom

I don't see how anyone can argue running 2 engines to do a given job can be cheaper than running one. Mind you, the OP didn't ask which was the cheapest

 

[Galaxy]

Thanks for all the great replies. I've been reading all the responses and taking it all in. It's a lot of info. I was confused why some people will have twin engines and then shut one down to get better fuel economy. Why not just run them both slower?

 

[MapisM]

I was confused why some people will have twin engines and then shut one down to get better fuel economy. Why not just run them both slower?

Been there, done that.
You do get a somewhat better fuel economy by not keeping heavy bits of iron spinning with no real need for the power they COULD generate, when you actually don't need it.
Which is exactly what happens at slow displacement speeds.
But there's more than that behind the principle - proven by countless installation on commercial boats and ships - that a single engine is better than twins in a monohull displacement vessel: easier maintenance, better u/w gear protection, larger prop, lower CoG, etc.
In practice, even if you DO get better fuel economy by running a twin engine boat with one engine at a time, you rarely bother doing that.
Fuel burn is reasonable anyway, with full D boats, and obviously twin engine boats run better with both engines on, rather than with an asymmetrical thrust - not to mention that maneuvering can be a nightmare.
Btw, in one occasion, I actually HAD to use the boat with just one engine, 'cause one engine was temporarily disabled.
More about that in this thread, if you're interested: http://www.ybw.com/forums/showthread.php?325343
And before anyone points that out, no, that experience is NOT a proof that 2 is better than 1.
In a single engine boat, I would have never let that water pump reach the point of getting useless.

 

[Galaxy]

Been there, done that.
You do get a somewhat better fuel economy by not keeping heavy bits of iron spinning with no real need for the power they COULD generate, when you actually don't need it.
Which is exactly what happens at slow displacement speeds.
But there's more than that behind the principle - proven by countless installation on commercial boats and ships - that a single engine is better than twins in a monohull displacement vessel: easier maintenance, better u/w gear protection, larger prop, lower CoG, etc.
In practice, even if you DO get better fuel economy by running a twin engine boat with one engine at a time, you rarely bother doing that.
Fuel burn is reasonable anyway, with full D boats, and obviously twin engine boats run better with both engines on, rather than with an asymmetrical thrust - not to mention that maneuvering can be a nightmare.
Btw, in one occasion, I actually HAD to use the boat with just one engine, 'cause one engine was temporarily disabled.
More about that in this thread, if you're interested: http://www.ybw.com/forums/showthread.php?325343
And before anyone points that out, no, that experience is NOT a proof that 2 is better than 1.
In a single engine boat, I would have never let that water pump reach the point of getting useless.

Thanks for that link. I'll check it out.