One Engine or two

[Portland Pirate]

I need some advice regarding outboard engines.

The boat I am about to buy has a single 115hp outborad fitted. However it is capable of taking twin outboards.

What I want to know is apart from the obvious advantages of extra manoeuvrability and the safety of having twin engines, what other advantages can you gain from having twin engines.

I know this may sound dumb, but does it mean you use twice the fuel for going at the same speed, or is there some formulae to work out the difference if there is any. If you are using twin 100hp engines is it the equivelant of using a 200hp single engine.

Any help would be much appreciated.

Sean.

[Portland Jon]

Hi Sean

Always have a spare engine and don't go anywhere that your spare can't get you home from. Our spare is 4hp so we still stay around the harbour even though we have a 20hp as the main one.

Jon

[Lookfar]

Hi Sean,
Twin engine set-ups are a bit of a luxury IMO. They're usually a lot more expensive to buy and to run than the same total hp in a single engine, and in general a lot heavier too. Fuel consumption is broadly speaking a reflection of the work done, so two 40hp engines 'should' propel a boat along at a given speed with the same efficiency as a 80hp single. However, you've got more weight, two legs adding drag and so on, so the twin set-up will be more thirsty, especially if the throttles or steering are not properly in sync. If you operate in an area that's very remote, go well offshore or into high-risk areas like close under cliffs then the extra security of twin power units may be worth the financial penalty. Otherwise, I'd personally place my faith in the reliability of modern engines (and the RNLI) and stick with a single unit plus an auxiliary.

Steve

[cod fisherman]

before i bought my boat last year i done some enquiries into using two out boards at the same time and was told by a dealer that the boat wont go any faster with one or two engines as it only goes the speed of the prop
but you will definately need a backup engine .
i use a seagull 4hp it pushes my boat at about 4.5 mph .

[Portland Pirate]

Originally Posted by Lookfar

Hi Sean,
Twin engine set-ups are a bit of a luxury IMO. They're usually a lot more expensive to buy and to run than the same total hp in a single engine, and in general a lot heavier too. Fuel consumption is broadly speaking a reflection of the work done, so two 40hp engines 'should' propel a boat along at a given speed with the same efficiency as a 80hp single. However, you've got more weight, two legs adding drag and so on, so the twin set-up will be more thirsty, especially if the throttles or steering are not properly in sync. If you operate in an area that's very remote, go well offshore or into high-risk areas like close under cliffs then the extra security of twin power units may be worth the financial penalty. Otherwise, I'd personally place my faith in the reliability of modern engines (and the RNLI) and stick with a single unit plus an auxiliary.

Steve

Thanks for the sound advice Steve. How is lookafar nowadays? have you dented any more props I regret getting rid of Maximus. If I could afford another Arvor 25 I would certainly get one.

Sean.

[Lookfar]

Hi Sean,
Lookfar's long-gone, I just have not bothered changing my forum name. I replaced her with a Pro Angler, had a catastrophic hull failure courtesy of an out-of-spec trailer and Warrior replaced it under warranty with another 165 (my choice). No more prop damage, I kill hulls instead these days

New boat's called SeaMouse, not really had chance to fish from her much yet but that'll change as soon as the weather eases off. Still running that Garmin plotter of yours though! What boat are you thinking of putting twins on?

Steve

[Hoggy]

......If you are using twin 100hp engines is it the equivalent of using a 200hp single engine..... Well apparently it’s not, this is only going by some info that was posted on a marine engine site and the name of that site escapes me at the moment.

I recall it stating that twin engines equates too approximately 80% …. So two 100hp motor would be equivalent to 160hp single engine, so this site reckoned, whether it true I’m not sure.