How to upgrade from a small Mercruiser engine

[NavalOfficer]

Hello everyone,

I have a 1982 checkmate with a little 3.7 Mercruiser. I want to upgrade to a larger engine, like a v-8. can I get an adapter plate and use current drive (with new gear ratio)? Or should I to buy a whole new drive as well? Any threads on upgrading or anyone have some good ideas? Lessons learned?

Basically I like my hull, I just want to upgrade the powerplant. (yes, it's all about power)

Thanks and respect.

Frank

 

[95yj]

Re: How to upgrade from a small Mercruiser engine

It'll probably cost more to change the gearset in the drive that it would to replace the drive.

 

[Bondo]

Re: How to upgrade from a small Mercruiser engine

with a little 3.7 Mercruiser.

Ayuh,........

The most sensable,+ economical way to go is,........
Buy a Donor boat, with the motor/ driveline you Want,..........
Then Strip it,..... Then install it's driveline into your Hull.......

 

[Don S]

Re: How to upgrade from a small Mercruiser engine

New drive (different gear ratio), new exhaust Y, new engine complete with exhaust manifolds to fit the Y, new inner transom plate, motor mounts on the stringers for a V8. The V8's don't use the front mount. The engine cover probably won't fit over a V8.
Basically, the transom shield is the only thing that will remain the same.

 

[TilliamWe]

Re: How to upgrade from a small Mercruiser engine

Frank my dad did a swap like this for a guy in Florida. DonS' parts list was right on. But he did find it all used and it wasn't terribly expensive. I think parts labor and everything, my dad charged him around $5000. He did fabricate a front motor mounting system too.
The guy didn't change his gear ratio in his drive, he just needed a much higher pitch prop.

 

[NavalOfficer]

Re: How to upgrade from a small Mercruiser engine

Thank you very much for the detailed answer! Sure appreciate you taking the time as I know how repetitive these boards can be. I love restoring anything with an engine, will take this down to parade rest and build it backup, play with it for as long as it holds my attention....and bam! it's on ebay and a great boat for the non-mechanically inclined person as I just examined it bow to stern) pays for the bad habit of loving to restore anything with an engine.

If I decide to upgrade, I?ll probably lay stringers and stick a 454 or a 460 in it with a jet drive, but that seems a little hard...only due to the lack of stringers. Jets don?t need much. bet she'd push 75!
I really do like the cockpit layout of this boat. I normally only have two seats!
I always start with the benign, the boat arrived yesterday and it?s already on blocks while I sandblast the trailer and run all new wiring/bearing inspections and such and add about ?5 position lights on each side?...gotta look good at night! And I love it when a trailer glows under water.
Thanks and respect

frank