84 chris craft 3.8L to 4.3L swap

[Spicy_McHaggis]

I recently acquired a '84 chris craft scorpion with a 229 cu.in. 3.8L Mercruiser. The 3.8 is pretty much junk, I was wondering which if any parts would work from my 3.8 on the 4.3. I have found a couple of 4.3's on craigslist, one fully dressed and another $400 cheaper w/out exhaust manifolds. The full dressed engine is a OMC Cobra 4.3 V6 HO engine, and the one w/out manifolds is a OMC Cobra 4.3 V6 engine. is there a difference between the two and what parts if any would work??

Thank you in advance for any help!!!!!!!!!!!

 

[Gary H NC]

Re: 84 chris craft 3.8L to 4.3L swap

The only difference in the HO and the other 4.3 is a 4 barrel carb as far as i know.
I think the money you save on the one with no manifolds will be spent on a new set...
The Cobra use the "bat wing" style manifolds but there are aftermarket sets out there.

 

[Howard Sterndrive]

Re: 84 chris craft 3.8L to 4.3L swap

EDIT: I missed the mercruiser part the first time - my coupler comment was for OMC - sorry

exhaust manifolds the same. All cooling system should swap over as well as electrical. plus carb and intake if the 4.3 is pre balance shaft and pre vortec

Distributor is NOT the same though. 229 has a different firing pattern than the 4.3

 

[Spicy_McHaggis]

Re: 84 chris craft 3.8L to 4.3L swap

the 4.3 is a 1989 4.3V6 HO OMC Cobra engine, sorry but i'm kinda confused now. i have other people telling me it won't work that i'm going to have to glass in new motor mounts and all kinds of other stuff. I just want to know the truth, ya know?! is the coupler the same as mine or would i have to use mine?? I have everything from my original 3.8 the heads are just rusted in place and the block was full of water when i got it so i'm assuming that the block is cracked somewhere.(never actually checked or had it checked just assuming) Will the motor mounts work??

Thank you again!!!!

 

[Howard Sterndrive]

Re: 84 chris craft 3.8L to 4.3L swap

the mercruiser 3.8 motor mounts will work just fine on the 4.3. (same part number mounts for the merc 3.8 and merc 4.3) The OMC mounts if they're still on the motor will probably work too.
Some pre-balance shaft 4.3's came with a dampening mounts, but they aren't a must. - just a luxury to take some vibration out.

The 4.3 OMC Cobra batwing manifolds will not likely line up to your Y pipe, but not sure...so you might be buying a set of center riser merc style manifolds if the 3.8 ones are toast.

You can use your merc coupler on the 4.3, or just buy a new one.

 

[Spicy_McHaggis]

Re: 84 chris craft 3.8L to 4.3L swap

you are awesome!!!!!!!! thank you for all of your useful information!!!!

 

[Spicy_McHaggis]

Re: 84 chris craft 3.8L to 4.3L swap

are the heads for these engines the same?? i know the intake and exhaust manifold bolt up to them both but i didn't know if the bore was the same dia.

 

[Howard Sterndrive]

Re: 84 chris craft 3.8L to 4.3L swap

3.8 and 4.3 heads have different chamber volumes. no swap unless you are changing pistons.

 

[Spicy_McHaggis]

Re: 84 chris craft 3.8L to 4.3L swap

ok so, this swap does not work... The bolt pattern off the crank is different and the flywheel is 3 inches bigger than the one from my 3.8. This causes my coupler not to fit along with the bell housing. The bell housing causes the rear motor mounts not to line up and is in the way of the power steering cooling line. what did you mean by different chamber volumes?? i understand displacement but is the 4.3 a longer stroke or a larger bore dia.?

 

[Howard Sterndrive]

Re: 84 chris craft 3.8L to 4.3L swap

michigan motorz sells a conversion I think for that scenario, with a small dia flywheel for the later engine and coupler

 

[Spicy_McHaggis]

Re: 84 chris craft 3.8L to 4.3L swap

checking into it tomorrow. I called at 6 but no one was there that could answer my question. They said to call back tomorrow and speak with a service tech.

 

[Howard Sterndrive]

Re: 84 chris craft 3.8L to 4.3L swap

this is from one of their ebay listings - it's referncing the 3.0, but the parts should work for your situation as well
the crank change on the V6 was around 1987, whereas the 3.0 changed cranks to the new bolt pattern in 1990
*
12-3/4" late model flywheel - This flywheel is needed if you are replacing a 2.5L or 3.0L engine from a pre-1990 boat/engine. Pre-1990 fly wheels (which are 12-3/4") will not fit, bolt on, or work on post-1990 3.0L engines- the crank bolt pattern is different. The 14" fly wheel that comes with the engine will not work because it is too large for the pre-1990 bell housing AND the starter will not work with the 14" flywheel - you need to purchase a late model 12 3/4" flywheel which Michigan Motorz carries for $149. If your existing 3.0L engine is 1990 and later, then you do NOT need this flywheel.
*
Engine coupler - This coupler is needed for pre-1985 MerCuiser applications and pre-1990 OMC applications. Michigan Motorz carries this coupler for $149. If your existing 3.0L engine is 1990 and later, then you do NOT need this coupler.