Hi ,my son and I purchase a 1987 Capri Bayliner , four cylinder 140 hp, G.M. motor 20.5 ft, . This is our first i/o boat .Last year we had the boat out maybe 12 time?s , it run perfect. The heat gage went up very little ( below 100 % ) the gage will read as high as 250 % . The trouble started this spring when after a long cold winter I decided to start it up in the driveway. I had a 45 gallon plastic barrel, which I cut in half and filled with water, put my cobra outdrive in it and started up the motor, I ran it 3or 4 minutes and shut it off , it ran good. We then took it to the lake and it was running great, took it up to 30 mph. for about 5 min. and all of a sudden the motor started making a dieseling noise and stopped running ? Smoke was coming out of the motor cover as if it was on fire. My son was driving the boat and nether him or I was watching the heat gage which was as hot as it could get. Well I thought the motor was cooked. So we let the motor cool off and tried to start it a couple of hours later and believe it or not it fired up, it ran a little rough but it ran, Now a month has past and I bought a manual for the boat. I now know my trouble started in the barrel of water ( I?LL NEVER DO THAT AGAIN ) I got all the piece?s of impeller out the water intake by taping off one side of the screened inlet and putting the water muff?s on the other side and then sucking with my shopvac at the impeller canal it worked great. I now took the thermostat housing off and found two big piece?s blocking the inlet. I put a new impeller in and took it for a ride, it ran pretty good and still seemed to have a lot power, but at 30mph the heat gage is at 175% and if you go slow the heat gage will go right up to 200% even 225% , so this is where we are at right now. Also I did not mention that there was no thermostat in it and there?s still not ,ihave not taken the inlet hose off at the thermostat yet while running the motor.
it will be my next step . P/S If you have any idea?s of what else to check I sure would appreciate your help. gwr
it will be my next step . P/S If you have any idea?s of what else to check I sure would appreciate your help. gwr