Volvo AD41B Overheating Puzzle

" Has anyone seen this one? E

" Has anyone seen this one? Even though the temp gauge reads only 165 degrees F, the temp alarm on one engine goes off whenever I attempt to speed up past 8 knots. I thought perhaps air was getting into the raw water system whenever I started to plane, but I would think the temp would go much higher if that was the case. So far, I've changed the raw water impeller and the thermostats. I also checked the exhaust elbow and it's ok. But the problem remains. What should I check next? Thanks for any advise.
Larry in Honolulu "

I think I solved the puzzle.

I think I solved the puzzle. I switched the alarm sending switch from my port engine to the starboard and the over heating alarm went with it. So I replaced the sending unit and "voila" no more overheating alarms. I just hope the engines continue to run cool.