One outboard or two ??

[Mfc1955]

'Bassing' has asked the question on a previous post..when one has two outboards on an Orkney Day Angler 21, what is more cost/fuel/power efficient, running continuously together or singly at times??? I'm interested in the answer???

 

[Guest]

When I used to sell motors I was asked this more than once and I still don't know the right answer. It is a fact that two 50 HP do not give as much power as one 100 HP etc etc. I think the hull design, displacement or planing, sea conditions, load, all affect the answer.
But If a boat will stay on the plane on one motor it probibly is more effecient to do so, one other deffinate fact is that if you run two outboards on on seperate 5 gal - 20 liter- cans the port motor usualy runs out first by about 2-3 litres
adobe.

 

[jfm]

There's a massive amount of drag pulling the gearbox through the water at high speed, hence twin outboards use much fuel compared with a larger single engine, and that's why 2x50hp is not as fast an installation as 1x100hp as adobe said. So if possible, run one, but all depends if it works ok, if close enuf to the centreline, etc etc

 

[kimhollamby]

As has been posted here a twin installation of any kind is considerably less efficient than a single. By what factor depends on many variables but suffice to say you would be better off with a large single outboard and a wing get-you-home auxiliary on a lift bracket if efficiency is the name of the game.

On the pair of 50s versus single 100 example quoted, it is unlikely that you would get up on the plane using one 50 alone on a heavyish 21-footer, especially as the prop pitch will be more appropriate for power when both motors are running (ie too course).

Twins also proportionately more expensive to maintain but you cannot get away from the fact that they look more businesslike!

Associate Publisher ybw.com websites kim_hollamby@ipcmedia.com

 

[jointventureII]

I know someone with 2 X 25 hps on a Fastliner 19.
He says that when pottering around (picking up/looking for pots etc)
he uses one engine but when at higher speeds uses both at lower revs
I hope this helps.
Also, kimhollanby gave me this great fuel consumption estimator.
For every 100hp of engine (2 stroke petrol) burns about 9 galls per hour at full power