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Old 05 November 2006, 09:46   #1
Country: UK - Wales
Town: Bala
Length: no boat
Join Date: Aug 2006
Posts: 134
Single or Twins?


I was having a discussion last week about the relative advantages/disadvantages of a twin engine setup as opposed to a single engine kicking out the same amount of horses. For example 2x 75hp and 1x 150hp.

This is from a rescue boat angle... so I feel that the "fail safe" of having a second engine is quite important.

I was just wondering what your thoughts on the matter were?

How do twins handle/perform in comparison to a single?
Would the fuel consumption be comparable?
Is the weight increase substantial?
Also, what would be the smallest RIB you'd put a twin setup on?


whiteminiman is offline   Reply With Quote
Old 05 November 2006, 11:48   #2
Country: Canada
Town: Tobermory, Canada eh
Boat name: Verius
Make: Zodiac Hurricane 590
Length: 5m +
Engine: Yamaha F150
Join Date: Oct 2006
Posts: 1,345
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Originally Posted by whiteminiman View Post
This is from a rescue boat angle... so I feel that the "fail safe" of having a second engine is quite important.
I think you just answered your own question!

When I was planning for a new boat (Hurricane 590), I spent a lot of time researching this. Interestingly, both the Hurricane dealer and the folks at Mercury talked me out of it... increased cost (initial and ongoing maintenance), decreased performance (according to both of them, you get less speed from twins with same horsepower...) and increased fuel consumption.

In my case, the question was answered when a gently used boat came along already equipped with a single 150, so I bought that.

Having said this, if I was replacing the boat, I would still consider twins just for the redundancy. In 10 years, I have only had engine breakdowns twice. Both were major (blown head) but conveniently, both times I was close to home....

I think the other advantage of the twins is apparent when towing. If you are going to be using your boat as a rescue boat, presumably this is also an advantage.

I don't recall ever seeing a boat smaller than mine (5.9m) with twins, but I suppose they're out there. The width of the transom is probably the issue...

In Canada, I don't recall ever seeing a Coast Guard RIB that didn't have twin engines. Of course they don't need to worry about cost, but obviously they feel it's worth having the twins...

Pump it up and RIDE!
Stoo is offline   Reply With Quote
Old 06 November 2006, 19:16   #3
Country: UK - England
Town: worthing
Boat name: ribtec 535
Make: ribtec 535
Length: 5m +
Engine: 2x 40hp mariner
Join Date: Apr 2006
Posts: 22
We have a 5.35 mtr Rib with twin 40hp mariners on board.


Plenty of torgue and execeleration from twin props.

In the advent of a break down, you still have a totally independant Engine, petrol tank and speed controller to carry you along at 23 mph plus.

The complete reasurance of having a spare engine to get you out of trouble quickly,rather than a underpowered 5hp spare.


Slighty less power than a single engine due to the drag of two props.
I was told that twin outboards give you about 3 quarters of horsepower compared to a single unit.

Drinking more fuel, but not double the amount as the 2 engines are not working as hard as one.


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