Early powertrain swap.

[Rex Baker]

Hi, New member poster here. Come from boating family and have worked on cars/boats for many years. Hopefully I won't have to pester with too many questions but this in relation to a 'deal' I found. I bought a very nice, used, galvanized tandem ezyloader trailer, that I thought I'd use for my boat, a 20' glastron, now on a single. The 'problem' is, I had to take the boat sitting on the trailer with the deal. I was going to dump the 'hull' at the recycle center. It turns out the hull is a very nice, clean '91 bayliner cuddy (20', I think) & is sound but, every bit of the powertrain is gone. All controls are still in place & seem to work quite well. By what the person said that I picked it up from, it was a 4.3 engine but the 'hole is definitely mercruiser. I do know there are exchange issues with pre-aplha, alpha, bravo, etc., when exchanging parts among them but I have access (well, 200 miles away) to a 1974 bayliner/mercruiser 140 drivetrain, complete, in very good condition, currently in a very bad hull. I'm not the least bit worried about this being underpowered so that isn't really an issue.

So, my questions are; Will the hole in the hull for the outdrive (size/bolt pattern) between the 74 mercruiser out drive & the one that was originally on this 91 hull, match? I'm pretty good at fiberglass & fabrication so small differences don't bother me and I can weld up a new aluminum bracket & mount for the front mount/stringer. I'm also quite good at wiring/schematics so while I don't think I'll hit anything there insurmountable, are there any tips in that arena?

I welcome any & all other tips & would also appreciate a plain 'ol 'Are you nuts?', if this is a bad idea.

Thank you all for your time. I'll try to attach a picture of the 'new project'.
Rex

 

[Bondo]

Re: Early powertrain swap.

So, my questions are; Will the hole in the hull for the outdrive (size/bolt pattern) between the 74 mercruiser out drive & the one that was originally on this 91 hull, match?

Ayuh,.... Welcome Aboard,.... it'll be a slug, but Ya, it'll all bolt right in...

I'd go with glassin' in a front mount, instead of a metal fab...

Mount the transom assembly, lower the motor in, align it with an alignment bar, 'n build out the mount to fit That Point....

 

[Rex Baker]

Re: Early powertrain swap.

Ayuh,.... Welcome Aboard,.... it'll be a slug, but Ya, it'll all bolt right in...

I'd go with glassin' in a front mount, instead of a metal fab...

Mount the transom assembly, lower the motor in, align it with an alignment bar, 'n build out the mount to fit That Point....

Excellent news, thank you for your help. The 4's not ideal but the price is very right & it will make a nice economical cruiser. When I get the bug to go a little faster I've got an old kindsvatter w/a sideoiler.

Not sure what I'll do/make till I see the mount on that motor now but I'll figure something out! Who knows, maybe the stringers will be the same width & height between them! Miracles can happen,right? Thanks, again.

 

[Scott Danforth]

Re: Early powertrain swap.

actually, it will use more fuel than a V8 pushing that big barge unless your just idling along

 

[Rex Baker]

Re: Early powertrain swap.

actually, it will use more fuel than a V8 pushing that big barge unless your just idling along

Actually, that's exactly what I have planned! Loads of idling on the scenic Columbia!

 

[Rex Baker]

Re: Early powertrain swap.

Just an update on the swap I did on the '91 Bayliner/'74 outdrive. I don't know if it was because of the age difference of '74 vs '91, or if the v-6 vs the 140 have different mounts but, the outdrive was not a direct bolt up. The four lower out drive bolt holes lined up fine but the two upper, holes were 1 inch, too high on the hull. Not a problem, I just re-drilled the new holes and mixed up epoxy to coat the dowels I drove into the old bolt holes. I glassed them also but it really wasn't necessary as the outdrive completely covers the original hull holes. Pretty minor issue & I wish I knew if it was the years, or engine, but just a heads up if anyone else is looking at doing this.

 

[haulnazz15]

Re: Early powertrain swap.

Just an update on the swap I did on the '91 Bayliner/'74 outdrive. I don't know if it was because of the age difference of '74 vs '91, or if the v-6 vs the 140 have different mounts but, the outdrive was not a direct bolt up. The four lower out drive bolt holes lined up fine but the two upper, holes were 1 inch, too high on the hull. Not a problem, I just re-drilled the new holes and mixed up epoxy to coat the dowels I drove into the old bolt holes. I glassed them also but it really wasn't necessary as the outdrive completely covers the original hull holes. Pretty minor issue & I wish I knew if it was the years, or engine, but just a heads up if anyone else is looking at doing this.

It was because of the years. You went from an MC-1 drive to an Alpha. The spacing on the bolts changed for the 1977-91 version.

 

[Rex Baker]

Re: Early powertrain swap.

It was because of the years. You went from an MC-1 drive to an Alpha. The spacing on the bolts changed for the 1977-91 version.

That's good information to have, as I have some other folks curious about what the difference was. Thank you!

Finally got to river test it this last weekend. Except for brain fade on the tach only reading 3,000 rpm @ max throttle, trimmed out (v-6 tach in boat, now 4 cylinder powered!) I had 36-37 on GPS and it actually planes out pretty quick. From the sounds of the motor (never a good idea) I'd say it was in the 4,500 rpm range so whatever size prop that came on it will work ok for this boat. Have a 4 cyl tach to pop in for next time out. Not bad for an overall investment of around $800 total, though I will spend about $180 in materials when I reupholster next year.

Thanks all, for your help!

 

[81 Checkmate]

Re: Early powertrain swap.

Thats great on the boat. Happy Boating!

Thought i would throw this out there. Check on the back of the tach and see if it has a selector switch from 4 - 6 - 8 cyclinders.
Maybe, maybe not.

Good Luck!

 

[Scott Danforth]

Re: Early powertrain swap.

if the tack doesnt have a switch, if you can pull the cover off, there is a trim pot on the inside. adding a small resister can get it to read properly.