Compatibility problems with my new engine and my omc sterndrive

[edelahousie]

NEED HELP!!!!

I have a 1970 omc sterndrive stringer. It had I believe was a chevy 305 powering it. I pulled that engine and purchased a 2006 chevy 350 marine engine. I figured chevy was chevy if you know what I mean. I went to bolt on the old drive coupler and found out the bolt pattern was different. Than I went to install the engine and it wouldn't fit in the bellhousing. The flywheel on the new engine had a bigger radius than the 305 engine. I need some serious help here. I have already put in alot of hours and money fixing this boat and sterndrive. I need some serious advice on what are my options here. I called the company who sold me the motor to see if they would exchange for another motor but met resistance. They said I could exchange flywheels, one that is the same radius as the 305 which is 12 and 3/4 inches. So I'm asking all you boaters out there please help. Thanks

 

[whywhyzed]

Re: Compatibility problems with my new engine and my omc sterndrive

Why try to fit it to the bellhousing with no coupler???

There is NO omc stringer coupler that will fit that engine. You need to get a different engine - earlier style pre 1987 engine with the 2-pc rear main seal design.

Your original engine was a 307, not a 305.

 

[Bondo]

Re: Compatibility problems with my new engine and my omc sterndrive

Ayuh,....... You've found 1 of the subtle Differences in SBCs,.....

As Noted, 1986 was the Last year of the 2 pc. rear main seals,+ the Large Crankshaft Bolt Pattern.......

Finding a 12" Flywheel for the new motor Still won't Help you because Nobody is making Couplers for those Old OMCs........
Atleast Not with the 3" bolt pattern......

About the Only Way out now, is to Resell the motor you've Got,....
And buy a Rebuilt Pre1987 motor........

 

[Limited-Time]

Re: Compatibility problems with my new engine and my omc sterndrive

Is having the current flywheel drilled and tapped for the original style coupler not an option?? Or would there be dynamic balance issues? Any good machine shop should be able to do it with little trouble.

 

[Bondo]

Re: Compatibility problems with my new engine and my omc sterndrive

LT,....... The Flywheel really Isn't an Issue,.......
Chevy still has only used the 12",+ the 14" Flywheels, both Before,+ After the Switch in crankshaft Bolt Patterns..........

It's the Coupler that is 3,1/4",+ the 1pc. Seal motors are 3".......

I Suppose you could have a Machineshop build you a Custom Coupler...........
I Bet it Wouldn't be Cheap...................

 

[edelahousie]

Re: Compatibility problems with my new engine and my omc sterndrive

Thank you all for the response to my problem. I should have thought about it before I bought the engine. Live and learn I guess.What do you think would be better, selling the engine and getting the right engine for this sterndrive or if I understand right I can use the smaller flywheel and have a machine shop take care of the coupler for me. If I go the route of using a smaller flywheel and getting a coupler to work with it , would the engine work than. Also what about the issue of the starter? I work in a machine shop, not as a machinest, but a welder and fabricator. But I have access to what ever machine work i need done. IF this were your problem what would you do. Thanks

 

[Bondo]

Re: Compatibility problems with my new engine and my omc sterndrive

Is your New Block Drilled,+ Tapped to accept the Straight Across Bolt Pattern Starter,..??..??....

 

[whywhyzed]

Re: Compatibility problems with my new engine and my omc sterndrive

What do you think would be better, selling the engine and getting the right engine for this sterndrive

That one, yes.

Where's your old 307?
Buy a old 350 out of a truck, or a long block from rapido or michigan motorz, swap all the marine stuff over from the 307- pop brass core plugs into it (the 2 on the back at least), rebuild and replace stuff like carb and ignition components and go.

 

[Windykid]

Re: Compatibility problems with my new engine and my omc sterndrive

I work in a machine shop, not as a machinest, but a welder and fabricator. But I have access to what ever machine work i need done. IF this were your problem what would you do. Thanks

Why didnt you rebuild the old motor?

 

[edelahousie]

Re: Compatibility problems with my new engine and my omc sterndrive

thanks guys for all the advice, I called a couple of the marine engine suppliers and they said they could get me the flywheel I would need. But I'm still not sure what road to go down. I would have to put the engine on ebay to sale it, and could take the 307 to be rebuilt. I just thought a new engine would be the way to go.
One other problem i have is on the sterndrive. Its a omc high profile and i just got done going through it from top to bottom.I put all new seals and everything. The problem is the driveshaft seal on the intermediate housing. I filled it with oil and it leaks. Did I do something wrong?

 

[whywhyzed]

Re: Compatibility problems with my new engine and my omc sterndrive

I called a couple of the marine engine suppliers and they said they could get me the flywheel I would need.

what good would the right flywheel be without a coupler to connect the engine to the drive?

I filled it with oil and it leaks. Did I do something wrong?

You have to fix the leak obviously. I can't understand what the high profile drive has to do with this.... If the intermediate leaks that noticeably, the boat will actually sink. It's that intermediate oil seal that keeps seawater from pushing through the theintermediate oil cavity and through the front lip seal into the bilge..