Some of you have read my posts and responded and I thank you but nothing was effective. I'd done everything short of tearing the heads off. However, I found the problem accidentally.
My engine would overheat at 3,000 rpm but not at idle or at WOT. This made tubing impossible and mid-range cruising difficult. Either too slow or too fast for the family. I had done the water pump, T-stats, poppet valve etc in the past and barring an unknown blockage, everything was as it should have been. Yet this aggravating issue this year.
I decided to pull the lower unit to check the water pump. I had eaten some sand at the end of last year but it didn't cause any issues then and I ignored it. But thinking there may be some wear on the impeller I decided to check it.
I dropped the L/U and instantly found the problem. It was my fault but I've never seen this before and I feel pretty dumb. When I slid the L/U up last time while doing the water pump, I misaligned the tube that runs from the water pump up to the metal tube that comes down from the powerhead. It had gotten close but the metal tube caught the edge of the plastic tube and had made two nice slits down the side of the plastic tube. So, only about 75% of the water was going up the tube- the rest was shooting out the two little slits. So I'm guessing that at idle when there was no load on the engine it was getting sufficient water to cool. At WOT the pressure overcame the leak and provided enough for cooling. At mid-range when the water pressure against the intakes was low and the water pump wasn't buzzing along at high rpm, the water flow was insufficient for cooling and the overheat occurred. Upon seeing the tube, I replaced it and put everything back into place.
I was able to run the engine in the driveway to ensure proper operation but could not verify a fix until a sea trial. I got out last Friday night, ran the boat at all rpms for over an hour and the temp gauge never exceeded 175. That tells me that the issue is gone. However, a stint of tube pulling will give me the answer I need. It's nice to find a problem when looking for one and I think I found mine.
UFM82
My engine would overheat at 3,000 rpm but not at idle or at WOT. This made tubing impossible and mid-range cruising difficult. Either too slow or too fast for the family. I had done the water pump, T-stats, poppet valve etc in the past and barring an unknown blockage, everything was as it should have been. Yet this aggravating issue this year.
I decided to pull the lower unit to check the water pump. I had eaten some sand at the end of last year but it didn't cause any issues then and I ignored it. But thinking there may be some wear on the impeller I decided to check it.
I dropped the L/U and instantly found the problem. It was my fault but I've never seen this before and I feel pretty dumb. When I slid the L/U up last time while doing the water pump, I misaligned the tube that runs from the water pump up to the metal tube that comes down from the powerhead. It had gotten close but the metal tube caught the edge of the plastic tube and had made two nice slits down the side of the plastic tube. So, only about 75% of the water was going up the tube- the rest was shooting out the two little slits. So I'm guessing that at idle when there was no load on the engine it was getting sufficient water to cool. At WOT the pressure overcame the leak and provided enough for cooling. At mid-range when the water pressure against the intakes was low and the water pump wasn't buzzing along at high rpm, the water flow was insufficient for cooling and the overheat occurred. Upon seeing the tube, I replaced it and put everything back into place.
I was able to run the engine in the driveway to ensure proper operation but could not verify a fix until a sea trial. I got out last Friday night, ran the boat at all rpms for over an hour and the temp gauge never exceeded 175. That tells me that the issue is gone. However, a stint of tube pulling will give me the answer I need. It's nice to find a problem when looking for one and I think I found mine.
UFM82
