[Capt. Paul]

Hi Kevin,
I had a problem with overheating as well. Same engines. My port side would overheat if run much over 3100 rpm.
I changed the elbows, which are salt water cooled. They were due and rusty. No improvement. Ran Barnacle Buster thru the salt water system and changed raw water pump impeller, no change. Pulled the oil cooler and heat exchanger and had a shop clean them. NO CHANGE!
One day while poking around it looked like the hoses that run from the thru hull fittings to the raw water strainers was starting to crack and as a matter of maintenance, I decided to change them. After pulling the port side hose off of the thru hull valve, I opened the valve briefly to see what kind of flow was there. It seamed weak so I stuck my finger in the valve and there was a giant barnacle inside the ball of the valve.
Problem solved. The other work needed to be done anyway, but check your raw water systems carefully. When was the last time the risers/elbows were changed? Rust can plug them up slowly. Your cooler and heat exchanger could have crud on the raw water side. How old is you raw water impeller? Hoses have been known to delaminate on the inside thus restricting flow.
Chasing these issues can be a pain, but if your fresh coolant is clean, the problem is on the raw water side 99% of the time.
Good luck and let us know what you find.
Regards,
Paul