Mercruiser 120 vs 140 block

mmoenter

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Right now I've got a 96 3.0LX with a cracked block. I know everything else is in good shape (head, exhaust, carb, etc). I can get a complete late 70s 120 for cheap and was wondering if the blocks were similar to where I can swap my good parts to it or if I need to find a 140 block. Thanks!
 

Bondo

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Re: Mercruiser 120 vs 140 block

Ayuh,... There'll be differences, but nothin' that can't be overcome....
 

mmoenter

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Re: Mercruiser 120 vs 140 block

Do you know what the bigger (more challenging) differences are? I'm looking for a rather straightforward project of swapping the head, manifolds, carb, etc to a different block. Thanks
 

Bondo

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Re: Mercruiser 120 vs 140 block

Do you know what the bigger (more challenging) differences are? I'm looking for a rather straightforward project of swapping the head, manifolds, carb, etc to a different block. Thanks

Ayuh,... Right off the top of my head, the Coupler is gonna be different, 'n the Flywheel...
The crankshaft bolt pattern changed around 1990 or so...
 

mmoenter

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Re: Mercruiser 120 vs 140 block

The coupler & flywheel can be swapped from the 3.0, correct? If I kept the crank/pistons from the 120 would I run into any problems with the head?
 

Bondo

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Re: Mercruiser 120 vs 140 block

The coupler & flywheel can be swapped from the 3.0, correct?

No,... They WON'T fit....

The head shouldn't be a problem though...
 

mmoenter

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Re: Mercruiser 120 vs 140 block

Ok...thanks...so if I'm reading this right, the SIMPLEST thing to do (besides buying a new longblock) is to find a 140 block?
 

Bondo

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Re: Mercruiser 120 vs 140 block

Ok...thanks...so if I'm reading this right, the SIMPLEST thing to do (besides buying a new longblock) is to find a 140 block?

Ayuh,.... Of the Correct Vintage, yes...
 

mmoenter

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Re: Mercruiser 120 vs 140 block

I'm probably beating a dead horse here (and I apologize) but I came across a nice looking 1978 3.0 block for the right price ;). Would I encounter the same problems (coupler, flywheel, crank) or would my parts swap into it? This would be a bare block (no pistons, crank, etc...just block and crank caps).
 

Bondo

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Re: Mercruiser 120 vs 140 block

Ayuh,... Same deal,... Not really any good to ya....

Look for a Long block, post-1990....
 
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