Remove and clean out the oil cooler.

I seen it happen several times. I used a stiff wire and pushed it through and needle nosed pliers on the other stuff. I have even seen small rocks from the sand stuck in there.
You might be surprised when you look through it.

They are either plastic or aluminum.

The plastic ones are one piece with 1 SS plate and the aluminum body ones are 2 pieces with 2 SS plates.

Aluminum one is first on page, plastic is second on page.
http://boatfix.com/bykeywordmerc.asp...kit&texttype=2

Thank you for the clarification. I think I have the aluminum one. A merc dealer said it is no longer available but I'm happy to see boatfix has it.

Here is what mine looks like:

Fixed it!!!
 

Tried again to get to the oil cooler. It's not going to happen unless I pull the exhaust manifold.

I put everything back together and guess what? It does not overheat. Yeah.

The engine is running 10 degrees hotter than the other one, port = 145, sbd = 155, so I'm pretty sure I still have a restriction in the oil cooler.

If I can just get through the rest of the season, I'll pull it all apart this winter.

Thanks everyone for helping.:ernaehrung004:

oil cooler!!
especially if around low water levels and sand :(
I back flushed, removed hoses, new impeller and housings and still the same thing!
even went after the hose in the gimbal/drive connection.
nothing helped!
until i pulled the oil coolers off and found to have only 3 open channels!!!!
took a lot of coat hangers/patience and pushing-pulling and pounding to get them clean.
However it all paid off because now they run cool and I did not have to spend $287/each for replacements :(

Yea, sounds like me. As much as it's going to be a PITA, I think that is what I'll have to do. Since she's not overheating now, I'm going to wait until winter. That way it'll be even more fun since everthing will be nice and cold.

I have had similar problems
Problem was the feed hose to the sea pump was being sucked closed when it higher rpm when more suction was created - collapsing the hose.
The problem caused impeller failure and caused the pieces to be clogged at the cooler-back flushing eliminated the large chunks from the system-however there were some that were clogged at the thermostat-also there were some that "melted" their was thru the system.

Anyway, the hose would not collapse on the garden hose, just under a load when in the water under power. check that system for faults. Possible - trying to help
Good luck