3.8(229) swap to 4.3

[ndwellcraft]

I recently purchased a 83 with a mercruiser drive with water in the oil. My plan was to put a 4.3 i have in. What I did not know is the engine in the boat is a 3.8. Are these two engines interchangeable and if so are there any major parts that need to be purchased to make this work??? thanks

 

[abj87]

Re: 3.8(229) swap to 4.3

the cheapest route would be to throw another 3.8 in there. Why do you want to swap to a 4.3 the 3.8 is one of the best motors gm ever made.

 

[ndwellcraft]

Re: 3.8(229) swap to 4.3

I have a excellent condition 4.3 on hand.From other searching I read (source??) that the 3.8 is based on the chev 305 bore and stroke and 4.3 is on the 350 bore and stroke. My question is are the external dimention between the two the same. I beleive this is not the same 3.8 as say what was used in many of gm cars.

 

[proshadetree]

Re: 3.8(229) swap to 4.3

3.8 has the buick old pontiac bellhouseing the 4.3 has the chevy.Manifolds are diffrent.#.8 easy or 4.3 if you can find whole swap with bad engine.Or case down all parts a real pain.

 

[Bondo]

Re: 3.8(229) swap to 4.3

From other searching I read (source??) that the 3.8 is based on the chev 305 bore and stroke and 4.3 is on the 350 bore and stroke.

Ayuh,..

Even though the #s would lead you to believe that,...
It's simply Not True....

 

[abj87]

Re: 3.8(229) swap to 4.3

the 3.8 is a buick v6 motor designed in the late 50's, it was used in cars up to 2008 so finding a block wont be impossible. Its nothing like the 4.3.

 

[Howard Sterndrive]

Re: 3.8(229) swap to 4.3

Mercruiser never used any Buick motors as some are suggesting. The 3.8 is indeed the same bore/stroke as a 305 V8. The 3.8 and the 305 even use the same part number piston.
4.3 will swap in if it's a complete motor, but the exhaust manifolds will sit out a bit further due to the wider 4.3 heads and that will require some creativity around the Y-pipe to riser couplings.

 

[chiefalen]

Re: 3.8(229) swap to 4.3

This 4.3 it a marine motor?

If yes is it sitting in a boat?

If yes You have everything you need to switch over.

If a car motor is a different dog.

Than you will have to marinarize the motor. I don't know even if thats a word, if not i just made it up.

Than as posted you will have to get creative as to the y pipe and risers connections rubber wise.

I would find a donor boat with a bad out drive or floor whatever, but a good motor, and switch the guts to the boat you want to save.

Good luck.

 

[abj87]

Re: 3.8(229) swap to 4.3

Mercruiser never used any Buick motors as some are suggesting.

Orgionaly a buick design then the bore and stroke was increased.
http://en.wikipedia.org/wiki/Buick_V6_engine

 

[chiefalen]

Re: 3.8(229) swap to 4.3

That was nice reading.

Can we get back to the op question.

 

[Howard Sterndrive]

Re: 3.8(229) swap to 4.3

Orgionaly a buick design then the bore and stroke was increased.
http://en.wikipedia.org/wiki/Buick_V6_engine

but Mercruiser never used it. OMC used some Buick V6's in the 60's and until about 1972, but ALL Mercruiser V6's are Chevrolets.

The 3.8/229 cubic inch Chevrolet V6 is what this thread is dealing with, not Buick.

 

[chiefalen]

Re: 3.8(229) swap to 4.3

Look you posted you have 4.3 laying around.

It come out of a truck?

Put some brass freeze plugs in it, change the starter to a marine starter, same with the fuel pump, and carb.

You maybe can use the stuff off the old motor.

Flywheel also changed with the old motor. Coupler also.

Install it and the manifolds and risers.

Now you have to see what you have to do rubber wise with the exhaust.

Listen i would use a alignment bar to make sure nothing dropped and the motor and the drive line up.

Make sure the gimbal is still good and the rubber on the out drive is good.

Good luck keep us posted.

 

[MikDee]

Re: 3.8(229) swap to 4.3

I know that OMC used the Buick designed 3.8V6 in early models, but then being it's a Mercruiser (Chevy 3.8) V6, everything should bolt right up to the 4.3. Years ago, I swapped an 89' Caprice 305/4bbl into a 78' Chevelle with an original dead 3.8V6, everything bolted up, including the orig. Y-pipe!

The 3.8 Buick engine is good, I had a 4.1 version of this engine in a 1981 Caddy Eldorado, it was the best thing about that car, and I loved it! but a 4.3Chevy is even better in a boat because of the base higher horsepower rating, & extra torque. Plus the easy parts availability, over the Buick.