Yep, water in the oil

[Mitch7182]

Good afternoon all and thank you in advance for the help. I have been a long time lurker on here and finally have a question that I could not find the answer to.

I have a 1987 Mercruiser 3.0 140hp and a 1974 Mercruiser 2.5 120hp. I was wondering if I can put the 140 head on the 120 block?


On the 3.0-
There is water in the oil, all 4 cylinders are 140psi compression. The head looks good but there was water "bubbling up" where the head and exhaust manifold meet up where the rust is on the pictures. I do see where it looks like the block has been repaired. Possibly a crack and repaired with something and painted over? Please see pictures.

The 3.0 ran great all last season and I winterized it this year, when I went to summerize it, "milky oil" shot out of the valve cover tube connected to the flame arrester.

Any other possible solutions?

Thanks again for your help.

 

[jtmarten]

Re: Yep, water in the oil

Certainly looks like a repair was made to the block, so that could have failed. Could also just be condensation from sitting all winter. Run on the muffs until she's warm; if it's just condensate it'll boil off.

 

[cedarjunki]

Re: Yep, water in the oil

yes you can use a 140 head but first you need to tract down the actual source of the problem.... could be a simple head gasket, manifold gasket, head, block, manifold, riser.....start simple and pull the head and check the gasket..

 

[Mitch7182]

Re: Yep, water in the oil

Thanks guys,

Would the compression in all 4 cylinders be constant with a blown head gasket? Also, no water on the pistons. I am looking into the riser tomorrow night, what would I look for, to see if it has failed?

 

[system-f]

Re: Yep, water in the oil

Would the compression in all 4 cylinders be constant with a blown head gasket? Also, no water on the pistons. I am looking into the riser tomorrow night, what would I look for, to see if it has failed?

On my straight 6 (4 banger similar) it could. The water and oil passages could have blown on the gasket without affecting the cylinder gasket.

 

[cedarjunki]

Re: Yep, water in the oil

as for the riser....theres really no easy or correct way to test it....
pull it off, pull out the plugs on both sides (if it has them)
flip it over and slowly and carefully pour water into the exhaust port not spilling any anywhere....
let it sit overnight if needed but if its cracked water should escape and start filling the water port.

this is how a machine shop told me and its how i found the bad riser on my fathers...although he also stated its very uncommon.