4cyl to v6 engine swap? help

[in to deep]

Need some help here please! i am restoring an old 1979 19' open bow boat
it has it a Chevy 140hp 4 cyl and a OMC 400 out drive? i get that right
inboard outboard?
the unit that bolts up to the engine has a capped off exhaust port. since it is not being used i was thinking if possible about dropping a small v6 chevy engine
instead of the straight 4cyl. if this can not be done can some one tell me why?? my omc book shows the 400 unit bolted up to a v6
Sorry i have done alot off car engine swaps in my youth and i know the trany
does not care what is turning it! is this differant?? also i would like power steering is there some kind of after market setup for this?
at some speeds on this boat it is harder to turn one way then the other !!


thank you for all your help on this !!

 

[Bondo]

Re: 4cyl to v6 engine swap? help

if this can not be done can some one tell me why??

Ayuh,... Several things off the top of my head,....
A Chevy V-6 wasn't used with that drive, so the conversion parts aren't available....
It was a V-6 Buick..
The drive is an Antique, so Any parts for it are gettin' harder to find...
The gear ratio will be Way Off,+ makin' it up with a prop change ain't gonna happen either...

The steering problem can be helped by adjustin' the torque-tab...

 

[HorizonblueDK]

Re: 4cyl to v6 engine swap? help

It should be possible to drop a 4.3 V6 into your boat. You now have the 3.0L 4 cyl GM engine. This engine shares the same bolt pattern for the bell housing as all GM engines used for marine applications. 4 cyl, V6 and V8(small and bigblock) So you can bolt a 4.3 engine to your bellhousing. As you have noticed, the exhaust is not a big deal, but you will probably need to fabricate some tubing.

Your housing has also been used on GM V8 engines, thats why you have the plug on the SB hole.

The coupler from the old 4 banger can not be used on a 4.3, the boltpattern on the crankshaft is different. But a little machining will probably do the job.

I have mounted an old OMC bellhousing with GM boltpattern onto a 4.3 engine. The flywheel on the V6 is a little larger than the V8s this bellhousing was intended for, but a grinder can remove the excess material.

The only problem I see, is the gear ratio. Your current 4-cyl ratio may be a little to low. But afterall, there is not a big difference on WOT on the 3.0 and 4.3, so maybe it's not that big a deal anyway.

But the boat will not go faster, just because you switch to a V6 and keep the drive. Another drive is preferred if you want the setup to be perfect.

A powersteering kit for the Stringer drive is available, well, sometimes one is seen on ebay, at a high price.

 

[superbenk]

Re: 4cyl to v6 engine swap? help

The V6 in a Stringer boat used the 800 Stringer outdrive, not the 400. I think the gearing is different & beefier to handle the extra power. I'm not sure if the intermediate housing is also different between the 400 & 800. It may be. I'd be concerned about putting a V6 on a 400 (if it's even possible) as it may very likely tear things up. The 400 was only used with the 4 cyl 120 & 140 HP motors.

Seems like an awful lot of work & cost for an obsolete drive setup. If you're bored & have deep pockets, just replace the transom & put a Merc engine + drive + controls on it & enjoy having a setup that's still has parts available

 

[Howard Sterndrive]

Re: 4cyl to v6 engine swap? help

capped off exhaust port. since it is not being used i was thinking if possible about dropping a small v6 chevy engine

there is no water shutter (flapper) under the starboard side - OMC was too cheap to throw that $10 part in there on the inline setups, they let you gamble on that stupid cap to keep you floating...even though the intermediate is otherwise identical -(you can buy and install a shutter, but requires splitting the intermediate... easy, but time consuming)

my omc book shows the 400 unit bolted up to a v6

it shouldn't

i have done alot off car engine swaps in my youth and i know the trany
does not care what is turning it! is this differant??

Different, yes - because the 400 series lower unit (13 spline propshaft) is only durable to 140HP- and even at that, it isn't superbly reliable.

The Chevrolet (not Buick)V6 (229 cubic inch 1980-84, and 262 1985), were mated to the 800 series stringer drive which had a lower unit capable of 260HP, identified by a 15 spline propshaft

also i would like power steering is there some kind of after market setup for this?
at some speeds on this boat it is harder to turn one way then the other

you don't need p/s, you just need to adjust the steering tab on the rear of the outdrive and lubricate the trucourse shaft at the starboard side of the intermediate