Mercruiser 120 to 140 swap

[timmyg]

Hi Everyone, I just picked up an older ("83) Galaxy 18 foot bow rider and it has a Mercruiser 120. The problem is that the engine froze and split the block and exhaust man. The last owned striped lots of parts and left it out in the rain so the engine was full of water when I got it.
A friend gave me an old mid 70s tri-hul that the boat is rotten but has a good running Mercruiser 140 in it.
Should I expect to run into any problems swapping these two engines out and will most of the parts swap from one to the other like the outdrive and hyd. parts?
I've been searching and it seems that these are both the GM iron duke motors. Is this correct?
Are there any links to some good info on these engines and outdrives?

Thanks, Timmy

 

[Fishermark]

Re: Mercruiser 120 to 140 swap

It should be a fairly easy swap.

The problem with the "Iron Duke" name is that it means different things to different people. Bottom line for boats - not many parts will transfer between an automobile 2.5 engine and these two engines. The good news? Most everything on the two marine engines will swap back and forth with ease.

 

[kadesdad07]

Re: Mercruiser 120 to 140 swap

I agree. It should be easy. I have a 140 in mine and the only diff that I chould find was in the bore and stroke of the 2. Everything else seemed to be the same. Hope the swap goes well.....good luck.

 

[Bondo]

Re: Mercruiser 120 to 140 swap

Ayuh,..... There are subtle differences,....
But,....
All the Bolt Holes line up with each other on both motors,....
They both use the same drive ratio too,.... Probably need a bigger Prop though....

This'll show you Alot of general Info on your motors,+ drives,....

And,......
This'll hook you up with All of the Merc manuals that are available on line,....

 

[timmyg]

Re: Mercruiser 120 to 140 swap

Thanks, This is what I was hopeing to hear.
And thanks for the links too
I'll be checking them out.
As soon as I get going good, I'll be posting pics.
and asking lots of questions.