had a problem ...returning from a sail, had the motor running at about2800 rpms for about20 mins the high eng temp alarm sounded. prior to the alarm sounding i noticed the exhaust got alot thicker and darker. checked the water flow to eng... seemed a little lite checked the filter coming into the line and it was clean. havent been able to re create problem but i havent run the engine that high since.....any ideas? any help would be appreciated