Mercruiser 3.0L 120HP vs 140HP (old) - compatiable?

Hello all,

I have searched the net high and low, and have yet to get a definitive answer...

I have a 92 bayliner with a 3.0L mercruiser 120hp. The block is cracked pretty baddly, so i have been searching for a new block at a good deal. I found one on craigslist only a couple hours drive away, but it is an older 140 Hp mercruiser. The owner says its 3.0L and 181 cu. in. My motor has thoes same specs, so i should be able to put all of my current engine parts into this old block, right? I did a visual comparison between the craigslist ad pics and my current block, and all the bolt holes seem to be in the right spot, right shape, etc. I know that i will have to use my current valve cover because it holds the shifting cable linkage, the older 140 valve cover does not have mounts.

I should mention that this guy has not only the block, but the crank, pistons/rods, and header as well.
Craigslist Ad: http://up.craigslist.org/boa/3230909438.html

Re: Mercruiser 3.0L 120HP vs 140HP (old) - compatiable?

I have a 92 bayliner with a 3.0L mercruiser 120hp.

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No wonder you are having problems, a 3.0L is a 140 or 130 hp rating, a 120 is a 2.5L engine. Also, 1989 was the last year the 120 2.5L engine was used.
Basically, you don't have a 120, you have a 3.0L engine.

I should mention that this guy has not only the block, but the crank, pistons/rods, and header as well.
Craigslist Ad: http://up.craigslist.org/boa/3230909438.html

Click to expand...

What a rusty mess that thing is. :facepalm:

It's also an older 2 pc. rear main block where your's is a 1 pc.

Keep looking.

Re: Mercruiser 3.0L 120HP vs 140HP (old) - compatiable?

^^^ Yup

That might be a pile of rebuildable cores, if they haven't been machined before and still have some "meat on the bone". The block isn't going to be compatible with 120HP internals, since the 140HP/3.0L is a stroked and bored 120HP.

Re: Mercruiser 3.0L 120HP vs 140HP (old) - compatiable?

Do you have a 2.5 or a 3.0? It doesn't make a whole lot of difference when replacing the engine but internals are different. Did someone put in a 2.5l 120hp before you got it?