I have a 1998 Mercury Optimax 135 that I recently purchased used. The engine temperature sensor comes on between 2,000 and 3,000 rpm, but if I accellerate to 4,000 rpm, the alarm goes off. I was reading the article about the tropical poppet valve on Kencan's motor; do you think this is a similar problem? the dealership claims that they have had a mercury rep in to look at it and that he has given it a clean bill of health. Every time they have operated the boat, they couldnt get the alarm to come on for them. I can get it to come on at will. Any info would be greatly appreciated.