Galaxy - Swap Broken 120 motor for Working 3.0 Questions

[cat3mann@gmail.com]

Ok...when you are done crying or laughing, either for me or at me, respectively...or both, I have to admit, as a newbie, I'm overwhelmed at the resources here yet unexplored by me but considering I've just retired and already haven't enough time left to fish, forgive me if I cut to the chase and prove myself a fool right up front rather than put you all through a long series of posts before I make it obvious.
With that said...
I have a question that could save me a lot of time of someone could clue me in.
I have two galaxy boats that I'm trying to make one galaxy out of. Both are Gm engines. One is a 120 block I.d. series NB and the other is other is a later model 3.0 series RX.
The bolt pattern appeared the same, are these motors exchangeable. I'll need to find info on this 3.0L. The old 120 is shot and the hull on the 3.0 is shot...have grandkids...need to fish.
Any insights from and we'll meaning source would be greatly apprecuiated.
Thx...Chet

 

[GA_Boater]

Welcome aboard, Chet.

I'm moving this to the IO non-repair section and adding to the topic title for clarity.

Are both motors by the same manufacturer? Not GM, but Mercruiser. OMC, Volvo-Penta, etc.?

 

[cat3mann@gmail.com]

Some bit of confusion there for me. Listed are the block I.D. numbers for motors that are both stamped GM and when searching I found listings for both GM and MerCruiser stern drives?
The 1980 hull has the 3.0. The RX series was only produced in 1998. So it's obviously not the original, however my research also shows my hull originally had a Model 120. The new a 1985 hull has what I believe was the original and it is a 120. More confusing still is the outdrive unit on the '85 has 3.0Liter MerCruiser Labeling ? Leading me to believe that they are interchangeable ? I wish I could be sure before going any further.

 

[GA_Boater]

Are both outdrives Mercruisers? GM didn't make stern drives. GM supplied the motors and the outdrive maker added the the propulsion bits, some unique parts and paint to make the motor a "Mercruiser".

 

[cat3mann@gmail.com]

He's...both out drives are marked MerCruiser. That's what threw me. The serial #'s on the out drives give confusing data http://www.marineengine.com/mfr/mercruiser_models.html This page shows GM 4 CYL outdrives and Mercruiser 4 CYL outdrives? My 1980 shows a 120 for that year but the block I.D. says it's a RX...1998 3.0Liter ? There is a 120 in my 1985 boat and that jives with the #'s on the outdrive but that drive is clearly marked 3.0 Liter "4" ? I can't get more confused, especially when you consider these boats are both so old there is no telling if any of the components are original ? Are ANY of these components interchangeable?

 

[GA_Boater]

Can't help ya with the interchangeability of the motors. I'm just not up on the stern drive stuff. Hopefully some one in the know will pop in.

 

[Bondo]

The bolt pattern appeared the same, are these motors exchangeable.

Ayuh,..... Welcome Aboard,.... They are exactly the same block, Externally,....

A plug, 'n play swap,....

The outdrives are Merc, 'n Merc buys long blocks from Chevy to power their outdrives,...

The 3.l is basically a bored, 'n stroked 2.5l,....
Only external difference is, the 3.l has a harmonic dampener, 'n the 2.5l has just a front pulley,...

 

[Scott Danforth]

there was a change in 1991 to the crank, so take all the stuff on the later 3.0 motor (including flywheel and transom plate) and move over to the hull with the busted 2.5 liter.

 

[cat3mann@gmail.com]

Thanks for all the help. The 3.0L I have is a great little motor and the galaxy fantail is the perfect hull for my area...all that's left now is the work...and no amount of time or money will ever change that, I reckon.

 

[Fishermark]

You should see a marked improvement of the 3.0 liter over the 120. (Not sure if you used the boat with the 120 or not). But yes, as mentioned, it is going to be fairly easy to swap out the two and make one good boat. Especially since it sounds like you have two complete boats to start with. There's always something that is surprising and has to be changed... but good luck with the swap.

...have grandkids...need to fish.

Amen to that!

 

[GA_Boater]

I was sure the 120/3.0 was a fairly easy swap, but as I said, I'm not that much up on Mercruisers. Sounds like you have some work ahead, but not too much.

Get the grandkids fishin', Chet.

 

[cat3mann@gmail.com]

Thanks again to all for the help. I'm sure I'll be back with more questions as this project moves forward.