3 outboards vs. 2 inboards

[Chiel]

Hello everyone,

I have come up with the next thing. We are outfitting boats with 3*250 hp outboards. The boats carry weight and are very Deep V. (deadrise approx. 24 degrees). I started wondering if twin inboards would be more efficient when looking at torque, fuel effecieny thus range, servicing and durability.

For comparison: 3 * 250 outboards - 2 stroke against 2 of the Mercruiser 496 HO 425 HP with bravo 2s on.

What will be the difference? Torque figures are not easy to get, so what will this do? Fuel comsumption is obvious I think... Inboards should be more efficient. Power to weight ratio? Durability of the Bravo since we have found them not suitable for commercial use on the powerfull diesel engines.

Diesel is not an option.

Any suggestions?

[hilux38]

I hope you own an oil company....(3x 250hp 2 strokes)

you should get a longer life out of the inboards, plus don't have to pay for 2 stroke oil.

[Chiel]

I'm trying to get married with mr. Shell's daugther

[BrianW]

I've often thought that three outboards might be a good idea for a 35-45ft drop bow landing craft, like a http://www.billmunsonboats.com/3240packcatphotos.html.

I was thinking (and I'm just a mechanic/fisherman, not a designer) that various combos of the powerplants could be used at different times. Such as all three engines when running a max load. Tilt up the center engine for normal cruising, or even crazier yet, trim up the two outboard engines and run one the center motor. Maybe the center engine could be bigger than the two outboard engines?

I don't know, heck it's probably already been done and proven to be a failure. I know my friends look at me a bit strange for even mentioning such a thing.

You are not crazy on your logic. All you say about running different engines was done in WW II on the PT boats. 1 eng. for sneak in. 2 for cruising. 3 for a torpedo attack or evacuation of wounded. Right on Brian!! As you get older you notice the only thing that really changes are the claims by the PR and sales people.