Advice on replacing io engine

[geezer]

Found out I've got a cracked block. 2.5 liter 120hp mid seventies mercruiser in an 18' Starcraft. Want to know if later 3.0 liter 130/140hp engines have the same dimensions so as be a direct easy fit. If so it would make many more used engines as prospective swaps vs just looking at 120s. I'm sorta close to OO, anyone know who might have a fair priced engine? Also need to know if my out drive would fit any engine. It must be an early one, does not say 'alpha' on it. Boat is a '73, engine allegedly a few years newer. Thanks for any advice.

[geezer]

Anyone got a good used or rebuilt 2.5 liter 120 hp mercruiser engine for my early 70's Starcraft?

[rolmops]

The blocks are the same size. Just make sure that the outdrive has the proper gear ratio for the engine that you plan on getting. There probably is a difference in the way the manifold connection to the exhaust looks. Yours is sort of rectangular and (upside down) U-shaped,while the newer 3 liter blocks have a round exhaust connection that does not go straight back but is offset at about 45 degrees. You will have to use the old engine u-shaped connection. It will either fit on as is or you will need an adapter.  But before you buy,you may want to get in touch with L&M (Hank). He does magical things with cracked blocks.

When you remove the block you have a very good opportunity to check the transom.

Edited January 4, 2016 by rolmops

[henrybud]

Give "Independent Marine"  a call.  Bill is a great mechanic and may have leads for you.

[geezer]

Thanks. I don't know who/ where l&m hank is?

[rolmops]

try this:

http://www.lakeontariounited.com/fishing-hunting/topic/55405-merry-christmas/

 

That will enable you to send him a pm

[L&M]

Thanks. I don't know who/ where l&m hank is?

 

Check you pm's geezer

[frontrowjoe20]

I have a 1983 Citation 20ft  2.5 Mercruiser I/O. Motor has new head gasket, fuel pump, carb, thermostat, starter and others... runs great. only issues I have is with the outdrive chewing up the impeller.so I am selling the boat with easy roller trailer for $1500 OBO if interested. I need to make space for brand new boat in march so I am willing to work with you.

[frontrowjoe20]

check PM

[Xxx]

Geezer I had that exact same problem mine cracked on the back side under the exhaust manifold, I took the motor out, this was the reason the guy gave me the boat, stripped the the motor and took the block to a engine builder, he pressure checked the internal ways it checked out good, so he used a space age type cement and smeared the crack shut. That lasted for 4 years till I sold the boat and I still see it go on the trailer to our local lake. There's no internal pressure on a boat motor that is not a closed water system.

[geezer]

My 120 has significant water in the oil, so I believe the crack to be internal and unrepairable. I think I need another engine, would like to find one that runs so as to avoid expensive rebuild cost. Buying a cheap boat would be a good option but not at $1,500.00. Thanks for responses.

[mxz670ho99]

check ebay there is usually alot on there

[cyrility]

Could be bad exhaust elbows. Had same water issue long time ago. Water hits hot exhaust valve, ruins valve allows water into cylinder.