This motor will sound the overheat horn after running 5-10 minutes at or close to WOT in 45 degree lake water temperature. In 80 degree water temp last summer, it would sound the horn at mid throttle and on one occasion we had to come back in at idle to keep the horn from going off. In all cases, reducing throttle would shut the horn up.
When the problem first occurred, we replaced the water pump. We have flow out the tell-tale, but the horn still goes off. Steady on horn when activated ? not beeping. We have removed the water jacket covers, thermostats, temperature switches, and heads - cannot find any visual reason for the engine to overheat. I have done 3 separate tests in hot oil to each temperature switch. The port side temperature switch (1 wire) will close at 197-216 and open back up at 164-165. The starboard switch (2 wires) will close at 201-213 and open back up at 193-196.
The thermostats start to open at 125, and come full open shortly above that.
There is no excessive corrosion or crud visible anywhere. The rubber diverter tubes in between the cylinder walls appear to be in place and intact.
Are there any recommendations where to look next? I tried to shoot the engine with a heat gun while running, but couldn't really get on it safely during the time the horn would go off and by the time we got the boat slowed down to a safe speed, the horn had quit and the highest temp I could read was 136. Not a really good test. I can order the thermomelt sticks as instructed in the service manual, but based on the temp switch test, I?m expecting the 163 degree stick marks will be melted. In the meantime am wondering what could cause the engine to be overheating if in fact it really is getting hot. The temp switches seem to be saying that it should be hot when they go off.
Is there an actual temperature gauge that could be installed on this motor with the display up at the console so we could visually monitor the actual temperature while running? Any suggestions on how to verify proper flow of water from the pump and through the engine? Is there any possibility that a lean fuel condition could be causing the horn to alarm? I'm grasping at straws now on how to properly diagnose this problem. thanks...Jon
When the problem first occurred, we replaced the water pump. We have flow out the tell-tale, but the horn still goes off. Steady on horn when activated ? not beeping. We have removed the water jacket covers, thermostats, temperature switches, and heads - cannot find any visual reason for the engine to overheat. I have done 3 separate tests in hot oil to each temperature switch. The port side temperature switch (1 wire) will close at 197-216 and open back up at 164-165. The starboard switch (2 wires) will close at 201-213 and open back up at 193-196.
The thermostats start to open at 125, and come full open shortly above that.
There is no excessive corrosion or crud visible anywhere. The rubber diverter tubes in between the cylinder walls appear to be in place and intact.
Are there any recommendations where to look next? I tried to shoot the engine with a heat gun while running, but couldn't really get on it safely during the time the horn would go off and by the time we got the boat slowed down to a safe speed, the horn had quit and the highest temp I could read was 136. Not a really good test. I can order the thermomelt sticks as instructed in the service manual, but based on the temp switch test, I?m expecting the 163 degree stick marks will be melted. In the meantime am wondering what could cause the engine to be overheating if in fact it really is getting hot. The temp switches seem to be saying that it should be hot when they go off.
Is there an actual temperature gauge that could be installed on this motor with the display up at the console so we could visually monitor the actual temperature while running? Any suggestions on how to verify proper flow of water from the pump and through the engine? Is there any possibility that a lean fuel condition could be causing the horn to alarm? I'm grasping at straws now on how to properly diagnose this problem. thanks...Jon
