OMC motor replacement

[wvff525]

Well, I've got an 79 OMC 3.0L 4 cylinder 140HP with the 400 stringer. The block on the motor is cracked and after a whole summer of trying to get rid of the boat.....I still have it. My buddy who messes with cars and is a fairly good mechanic recently got an 88 2.5L 4cylinder motor from an Olds car. He seems to think that I can replace my 3.0L block with this 2.5L. So thats my question.....Can I??

Will it bolt to the 400 sterndrive?

He also mentioned something about using the head from the 3.0L on the 2.5L. It doesn't sound like it would work to me but....Obviously, I'm an idiot when it comes to motors. I would have to rely on my buddy for help, but I just thought I would ask before we tore into it. Thanks in advance.

 

[Haut Medoc]

Re: OMC motor replacement

Will not work......
The only thing that they share is the litre designation.....
They are not the same motor & will not be compatible......​

 

[whywhyzed]

Re: OMC motor replacement

Obviously, I'm an idiot when it comes to motors. I would have to rely on my buddy for help, but I just thought I would ask before we tore into it.

I'd say the buddy is more of an idiot with all the assumptions. You were smart enough to ask and now you know enough to not waste your time or money. It's a different engine- no common parts.

 

[wvff525]

Re: OMC motor replacement

Thank you! Now I have the pleasure to inform him he was wrong.

What motors will work for the OMC 400 sterndrive? Obviously..the 3.0L that is in there now...but are there any others? Since it seems...I'm stuck with the boat, I thought I might look into my options. If I can't find another motor, I might convert it to an outboard powered boat.

 

[Bondo]

Re: OMC motor replacement

Ayuh,........

There Are 2.5l Boat motors that are a direct Swap for your 3.0l,....
But,.......
As noted,... The 2.5ls used in Automobiles will Not fit.......They're Totally Different Motors......

 

[whywhyzed]

Re: OMC motor replacement

If I can't find another motor, I might convert it to an outboard powered boat.

nah, you'll find one - I sold a 2.5 marine engine this summer for $650 - it was like new - less than 100 hours on the thing.

 

[wvff525]

Re: OMC motor replacement

how about a Mercruiser 3.0L? will that work...or do I have to stay with OMC? Also is a 2.5L and a 3.0L my only options with the 400 stringer or can I go larger? Just trying to figure out what to search for. Thanks

 

[Haut Medoc]

Re: OMC motor replacement

how about a Mercruiser 3.0L? will that work...or do I have to stay with OMC? Also is a 2.5L and a 3.0L my only options with the 400 stringer or can I go larger? Just trying to figure out what to search for. Thanks

The Mercruiser is the same GM block, you will just need to bolt all of the OMC stuff on it......
If you use anything else you will be looking at serious modifications that can't be worth it on a boat that old......
Look on ebay for a 3.0 or 2.5 merc.....