I have had my 4.3 Yamaha since 1994 with no problems. In the last year I have gone through 3 Raw Water Impellers. There are no rough edges in the water pump housings the boat runs fine for about 1/2 hour temp remains constant then it sounds like the the pump is sucking air when you gun the engineto pull up a skier the temp rise 20 degrees then goes back to normal. the fins on the impleller break off. Could it be the intake hose cannot supply enough water, the thermostat is sticking open and i am pumping too much water than i can suck.
