Can I swap a 120 merc with a 135 merc?

BMK10

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Oct 26, 2016
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I'm looking at a 16 ft starcraft with a 120 mercruiser engine and I have a feeling the engine is shot so I'm wondering if I could swap out the engine with a 3.0l mercruiser from an 18ft starcraft, basically the same boat. I'm just wondering if the mounting brackets will line up as well as the outdrive..
Hoping someone can shed some light my way before I start this project
thanks
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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it will simply bolt right it. get the same vintage. 1990 and older or 1991 and newer (less things to swap)
 

Bondo

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Ayuh,.... Like Scott says, the Long Blocks are the same,....

If yer talkin' full dressed bobtail motors, maybe not, as there were changes through the years with the Merc add-ons,....
 

BMK10

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I don't think they're bobtail motors. I just did some googling to figure out what that meant to be honest haha. The motors are pretty much identical from what I can see so I'm assuming they're long blocks and all should be good.
 

Bondo

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Ayuh,.... A long block motor is just the block, the internals, 'n the head,...

A bobtail motor is a fully dressed, ready to drop into the boat, motor,...

A bobtail motor is the block, the internals, the head, 'n ALL the bolt on accessories that make it a boat motor,....
 

Scott Danforth

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And a long tail has the outdrive attached
 
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