Converting OMC to Mercruiser

[LTDan440]

Hi everyone.

I have an '81 Galaxy with a Chevy 3.8/OMC Stringer 800.

Im tired of trying to find parts for the outdrive so I picked up a rebuilt '99 Mercruiser Gen I/Alpha I with a 2:1 gear ratio.

I know I will have to work on the transom since the hole is about twice the size for the Mercruiser. Other than that, what else will I need?

Steering cable?
Throttle cable?
Can I use non-Vortec 4.3 exhaust manifolds on the 3.8? (Eventually I'm going to replace the V6 with a 350 Theres plenty of room on these old boats)
I dont have my OMC shop manual in front of me so Im not sure what the gear ratio is (1.77 maybe?) Can I make the 2:1 work?

 

[Reel Poor]

Re: Converting OMC to Mercruiser

If that's the 3.8 liter Buick motor, distributor in the front, you are going to need every conceivable part including an engine. Mercruiser didn't use the Buick V-6 in anything, the Buick bell housing bolt pattern is an oddball and won't fit anything Mercruiser built.

IMO, before you go through that much trouble, replace the boat.

 

[Don S]

Re: Converting OMC to Mercruiser

You also need to check some other things.
No such thing as an Alpha I Gen I in 99. The gen I (known only as ALPHA I at Mercruiser) production ended in 90. From 91 on it was Alpha I Gen II.
The 2:1 ratio, is NOT an Alpha drive.

 

[LTDan440]

Re: Converting OMC to Mercruiser

its a Chevy 229 ci V6; distributor's in the back. Despite it being the original engine, it runs excellent, has decent power for a 6, and still has good compression in all cylinders.

the seller told me it was a '99 Gen I-how can I verify what exact year and model it is? Also, how can I verify that 2:1 is the gear ratio? I got it extremely cheap from a guy that was upgrading to a bigger engine and I could easily sell it to make some dough. The OMC on my boat was rebuilt 3 years ago and I'll use the sale of that unit to finance the retrofit of the Mercruiser.

I'm not scrapping the boat-the hull is in excellent shape, has a new interior and electronics, and I'd rather spend a couple of thousand upgrading the drivetrain instead of a lot of thousands replacing the boat Besides I love them old boats and she's got a lot of life left in her

 

[Reel Poor]

Re: Converting OMC to Mercruiser

Get the serial number from the drive unit and post it here. The pic below shows where you should be able to find this information.

(a) is the serial number location
(b) is the drive ratio location

 

[Bondo]

Re: Converting OMC to Mercruiser

Ayuh,......

When refitting a hull,... You've got to scrap out ALL of the OMC,+ replace with Mercruiser......
Marrying the OMC Motor to the Merc drive isn't worth the Frustration......Nothing is going to line up...

If your set on doing this,.... Buy a Donor Boat,+ Swap the Complete, Whole Driveline, Motor,+ All.....

 

[whywhyzed]

Re: Converting OMC to Mercruiser

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