Donzi 4.3 to 5.7 motor swap help (need motor!)

[generallee01]

Hey all! I'm new to the forum but decided it would be a good time to join as I just purchased a boat after being off the water for a few years. I have an 89 Donzi Regazza 21 that I'm seeking some advice on. when I tell my friends I bought a Donzi they are suprised to hear it had a 4.3 in it! I was too. At any rate I pulled the motor the other day and it's toast. What I've learned so far is this....the cobra outdrive will work but may need to be re-geared, the bellhousing will bolt up no problem. I need to know if I will need to either swap the motor mounts....or move the motor mounts. I really dont want to move them and have to worry about allignment. If it requires moving them I may just drop another 4.3 in it. Anything else I should know? Will mopst of the accessories from the 4.3 work on a 305 or 350? Thanks for all the help! -Pat

 

[Don S]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

OMC went out of buisness over 10 years ago, regearing may require buying a rebuilt unit on line or used someplace. Unless you have the special tools to rebuild a drive, you can't do it at home.

Will mopst of the accessories from the 4.3 work on a 305 or 350?

Alternator maybe, but that's about it.

I need to know if I will need to either swap the motor mounts....or move the motor mounts.

Depends on how the 4.3 stringers are designed, the mounts on a 5.0 or 5.7 is further forward than a 4.3. Alignment is adjustable.

 

[Bondo]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

I really dont want to move them and have to worry about allignment.

Ayuh,...

You've Already gotta be Worried about the Alignment,..
You pulled the motor,+ Reinstalling it Requires Realignment,... Period....

 

[chiefalen]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

What you really have there is a hull if you want to go with a bigger motor.

Want to keep that hull, buy a donor boat with the package you want in it, but not a omc.

And transfer over the package to that hull you want.

Just my 2 cents.

 

[generallee01]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

Thanks for all the input guys. I guess i didn't exaplin it right though. I'm well aware I need to realign the motor with the outdrive. I meant will the motor mount pads line up. Meaning, will I have to move and redrill the mounts elsewhere? As far as the Cobra outdrive is concerned...supposedly it only has about 5 hours of runtime on it. All in all I wouldnt be opposed to dropping a 4.3 back in. In a perfect world I'd find a great deal on a low hour used motor. I have a few months to be patient and look around. I could go out and buy everything I need but I'm making this boat my little budget resto project. It's come a long way even in having it 2 weeks! Thanks again, -Pat

 

[chiefalen]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

Least expensive way, get a omc 4.3 motor, fresh water used complete and drop it in.

Good luck !

 

[MikDee]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

Well, I can't speak for boat engines, But I'm betting it's the same as I found. I replaced an original 4.3 V6 in my 78' Chevelle wagon with an 89' Caprice 305 4bbl V8, I did have to get new mounts, but once I bolted the engine up to the bellhousing, the mounts just fell into place, meaning that the distance of the casting from the motor mount to the bell housing, on the V6, was exactly the same as the V8. The water pump, pulleys, power steering, alternator, and Even the Y-Pipe was exactly the same!
It was one of the easiest swaps I ever did.

 

[Don S]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

Meaning, will I have to move and redrill the mounts elsewhere?

Yes, the side motor mounts on a V8 are farther forward than a V6

 

[slasmith1]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

Did you consider that there is a different gear ratio needed for the 5.7 which would require a whole new drive?

 

[CarTuner]

Re: Donzi 4.3 to 5.7 motor swap help (need motor!)

I have a 1988 Donzi 23' Ragazza with a 5.7 OMC Cobra in it......real nice boat

Anyway, some parts from the 4.3 will swap over to the V8, like the water pump, alternator, power steering, thermostat housing, bellhousing, fuel pump, and even the motor mounts. But yes, you will have to redrill the stringers for the mounts of the V8. As most here have said, the V8 will place the mounts further forward versus the 4.3 V6.

The gearing is also different in the outdrive. The gears that need to be changed are in the upper housing; the lower housings (and gears) are the same between the V6 and V8 setups.