Logo
FULL SITE MENU

OMC 120 Seized Need Options

A

alex stanton

Guest
"I have a 1979 OMC 120 engine

"I have a 1979 OMC 120 engine which (with the help of everyone here) I came to the conclusion that it is siezed up. The boat has sat for over 10 years, and about 5 years ago someone pulled the spark plugs and let it sit outside.

The rest of the boat cleaned up very nice (new carpet and seats and we're back in business), I'm told the mechanical OMC 400 Sterndrives are pretty tough, and I'd like to get her in the water.

What are my options as far as engine replacement? I'm fairly mechanical, don't mind rebuilding an engine if I have to.

So I've been doing some research and it looks like the GM 2.5 was used in a lot of cars. Will ANY GM 2.5 or 3.0 4 cylinder inline bolt up to the OMC Sterndrive bell housing? If so I found a rebuildable GM 2.5 that came out of a FWD vehicle from the early 80's (Pontiac I think). Does the FWD factor make a difference?

Also, is there a Mercruiser branded engine that is a direct replacement for the OMC 120? A lot of people are selling mercruiser 140 GM engines and I am under the impression that these are the same as the OMC 120. I believe the water pump for my OMC is in the Outdrive... if I were to buy an automotive longblock would I be able to run it in a marine application?

Thanks all for your help, the boat isn't worth a lot, but it sure would be nice if I could find something economical to get it in the water at least for this year."
 
"only car engine's that mi

"only car engine's that might help you were the 1962 thru 1967 or so ChevyII and Nova 153 cubic inch....most of those have been scoured out of wrecing yards years ago for boat parts. As far a s Merc , yes they also used the same 153 cubic inch or 2.5L, rated at 120HP. And the 3.0,181 cubic inch motor, usually rated at 140HP whether Merc or OMC will replace your motor quite easily if pre-1990 unit is used. no automotive long blocks are compatible though. It's a funny motor that did originally come from that Chevy II, but was discontinued in cars around 1970 but continues in boats today. GM made several car engines with a 2.5L displacement, but they are different units"
 
thanks for the information. I

thanks for the information. I found a 140 merc engine that runs for 600 dollars. another forum suggested that I pull the outdrive (which I have to do to replace the engine) and see if the engine will crank with everything removed. think it's worth a shot?
 
yep..always a good idea...you

yep..always a good idea...you might also be smart to pull the intermediate shaft out the back once the drive is off if still wont turn
 
Back
Top