I have a 1994 powerquest 257 legend that a friend and I replaced the transom assembly / outdrive on. Took it out this past weekend and everything is running great until I got it on the trailer and I noticed oil ring behind the boat. When we had the engine out, I noticed that the oil cooler had froze and busted the braize on the endcap. I had this fixed and installed it. I am thinking that maybe when it froze, it damaged the oil passages through the heat exchanger. Is this possible? And how would I go about pressure testing? I sure hope it is just the cooler and not something more serious! I have read the oil coolers from mercury are cheaply made. Ofcourse anything will bust when full of water in the winter months. Thanks in advance for any replies!

you should just replace the cooler to be sure....not worth killing the engine over those..

You can bypass the water side of the cooler cooler with a piece of PVC between the hoses then run the engine for a little while (idle is fine) then check for oil in the water jacket. Or remove it, plug one side, air up the other and hold it under water to watch for bubbles. Fittings can be found at Home Depot.

Thats a great idea! I will without a doubt try that and check the water jacket. You are talking about the water jacket on the cooler correct? I forgot to mention in my first post that the block on this engine is cracked and repaired... I am afraid that the oil journals in the side with the crack are leaking into the water jacket on the block.... I'm just hoping that's not the case...

I am curious, you say the block had a crack and was repaired ! Repaired with what ?
Is your oil milky white ?
Was is a bad winterize job that caused your problems.
Good luck hope your problems are not big ones.
Brian

He never said the block cracked. He said the oil cooler popped an endcap.

Actually the block was cracked due to the previous owners half a** winterizing job. I have posted on other threads about the crack and how I put a "bandaid" on to get me through the season. The oil cooler did in fact blow the braize out of the endcap. I am pulling it tonite to pressure test. The oil is not milky or shows any sign of water contamination. I ran it all weekend and on Monday I pulled an oil sample to check for water content. The test came back negative hopefully I do have a bad oil cooler but I am having trouble finding that particular model at a decent price. Anyone know
Where I can get one? I believe it is special for the 502 but not certain. It is the one that cools both power steering and engine oil.

the cooler is leaking internaly . oil persher is more than water persher there for it forces oil into the water and it comes out the exaust . been there done that . replace it . MR cool . right here on oso . sponcer

I'd be happy to help. Call for some advice and if you're sure you need the cooler, we'll help with that.


Russ