Have a 2001 Bennington Tri Toon 2575fs powered by a 2001 Mercury Optimax 150. Motor overheats and bell sounds when at trolling speed. It will maintain 158 degrees but only when going at slowest speed. Temperature drops when at 1/3 throttle and above but the minute you reduce to a slower speed temperature climbs till bell sounds. Also boat's top speed is only around 25mph! Boat came with a Mercury Revolution 4 ( 4 blade ) 19 pitch stainless prop. Wide open throttle is 4040 rpm with motor trimmed all the way down. Cavitation also a problem when turning sharply. Local mechanic looked at boat and said middle pontoon was creating a channel of water in front of the "foot" of the motor causing the "foot" to be too high in the water. He said this would explain lack of speed due to lack of "bite", overheating problem due to intake of disturbed water, and the cavitation. Jack plate was recommended since motor at it's lowest mounting position. This problem has occured since new. Local dealer closed so no support avail. Anyone out there with same boat/motor combination? Same problem? Do I need Jack plate? Do I have correct prop? Any suggestions?
