We have a 1988 Sea Ray with a Sea Ray (Mercury S/N B278442)) 135 hp. After running for 5-10 minutes we get the steady alarm which I believe is indicating that it is overheating. The water temperature coming out is about 155° and the temp guage is reading around 145°-170°. Could it be either one of the temp sensors? I've been running a synthetic oil in it and I'm wondering if that might have something to do with it?
Any help would be greatly appreciated. Thank you!