OI drive Installing an outboard inboard

" O/I drive , Installin

" O/I drive , Installing an outboard... inboard

This is a post I placed on the Classic Boat Discussion Group back in Feb. with no response. I am hoping someone of this board *has some experience* and will offer opinions. I am not much interested in "I don't think I would try that" sort of responses unless there is experience to back it up


At this point, this is an exercise in "speculative engineering"; however, I would like to hear of anyone's experience along these lines.

I am considering converting a 1959 Fleetwood moulded ply runabout hull that I own into a step hydroplane with a high humped foredeck, as was sometimes done in the 30s.

I'm working on a novel (?) idea for an engine for it. I'd like to know if anyone's ever seen it done. First, I'm a fan of the Merc inline 6 cyl engines. I own 3 dock bangers now and have had two others in the past.

I am thinking of using a straight 6 as an inboard. At first, I thought of laying one of the dockbangers down and driving the prop shaft directly off the output shaft of the engine, obviating the need for a gearbox. But, I really want more than the 70 hp afforded by this solution, and I didn't want to have to make a water pump system for it.

Next, it occurred that any modern outboard foot has a FNR gearbox in it, so why not get a later 140 hp merc and remove the leg. Now, take a large engine foot, say a 235 hp, and mate it with an adaptor plate,and mount the whole thing vertically... really just a very short outboard engine mounted inboard.

I think that the water pump might not draw, so a lift arrangement still would have to be made. Another possible engineering problem would be cooling the foot, since it is designed to run in a cooling environment, but a water jacket for that shouldn't be any challenge.

Ever seen it done? I'd like to hear your opinion of it. BTW, the reasons for this are light weight and economy If I had a lightweight marine gearbox I'd probably do a straight inboard using an sutomotive-type V8. Still, the challenge of this arrangement is interesting.

Cheers/Don Carron
Rockford TN "

" John,

Since you are going

" John,

Since you are going through all this custom engine work why not have the "foot" protrude through the hull the way the saildrive arrangements do it. This would solve the pump problem and the cooling problem.

This may not suit your needs, but I think it is the easiest way to use an outboard as an inboard.

Tony "

" Tony,

the boat is a step

" Tony,

the boat is a step hydro. The prop needs to be at the transom.

Cheers/Carron "

"John.... A friend of mine, wh

"John.... A friend of mine, who is also a denist, has done exactly what you're wanting to do (I think)... converting a I/O Craft to a Outboard Craft. The hp of the I/O escapes me but the outboard version when he was finished was a 225hp Johnson. I might add that he did an excellent job from start to finish, both in strength preperation and finish quality.-->Gerald M. Boza, 2600 W. Sligh Ave, Tampa, Fl. A search of Gerald Boza will lead you to him immediately whereas perhaps you can compare notes. Tell him that his old outboard mechanic sent you. "