the fresh water buzzer goes off 15 minutes after running the engine. I replaced the thermostat, and took apart the water pump it looked ok. Also took apart the raw water pump and checked the impeller it also looked good. Anybody out there have had this problem?
Yanmar Hunter engine overheating
- Thread starter Anthony Scuria
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1. are you sure that the impeller is okay. Sometimes the rubber and the center may seperate and the water will not pump.
2. mixing elbow
3. belt tight enough
4. heat exchanger plugged
Have you drained your coolant? Possible air in the cooling system.
2. mixing elbow
3. belt tight enough
4. heat exchanger plugged
Have you drained your coolant? Possible air in the cooling system.
Assuming the overheating is real and not just a bad sensor.
If you are not getting enough cooling then either there is not enough raw water passing through or there is not enough fresh water circulating. The raw water seems to be more problematic than the fresh water.
One thing you can see just by looking is whether there is plenty of raw water coming out of the exhaust. If not then either there is a blockage somewhere, or an air leak into suction side, or the raw water pump is not doing its job. You can disconnect the pipe at the entrance to the raw water pump and hold it below the water line. Lots of water should come out. If it does'nt look for a blockage in the strainer or intake. Try back flushing it out with fresh water. Look for leaks or collapsing hoses on the suction side of the raw water pump.
If you don't find anything on the suction side of the fresh water pump disconnect the hose on the discharge side and try blowing through it. You should be able to fairly easily blow through the heat exchanger and the exhaust manifold and the mixing elbow. If you can't then disconnect between the heat exchanger and exhaust manifold and blow there. If that reveals a blockage try blowing through the mixing elbow. Somewhere with just lung power you should find the problem. Mine was a build up of scale at the exit of the exhaust manifold.
If there was plenty of raw water I would test by doing a run with the thermostat removed.
If you are not getting enough cooling then either there is not enough raw water passing through or there is not enough fresh water circulating. The raw water seems to be more problematic than the fresh water.
One thing you can see just by looking is whether there is plenty of raw water coming out of the exhaust. If not then either there is a blockage somewhere, or an air leak into suction side, or the raw water pump is not doing its job. You can disconnect the pipe at the entrance to the raw water pump and hold it below the water line. Lots of water should come out. If it does'nt look for a blockage in the strainer or intake. Try back flushing it out with fresh water. Look for leaks or collapsing hoses on the suction side of the raw water pump.
If you don't find anything on the suction side of the fresh water pump disconnect the hose on the discharge side and try blowing through it. You should be able to fairly easily blow through the heat exchanger and the exhaust manifold and the mixing elbow. If you can't then disconnect between the heat exchanger and exhaust manifold and blow there. If that reveals a blockage try blowing through the mixing elbow. Somewhere with just lung power you should find the problem. Mine was a build up of scale at the exit of the exhaust manifold.
If there was plenty of raw water I would test by doing a run with the thermostat removed.
Check the rubber hoses on the suction side of the raw water pump for collapse. Also check the raw water strainer.
It all started when my boat was launched as soon as I put water into my holding tank I noticed my hot water heater was leaking badly. I had a new water heater installed with all the hoses this I thought was the end of my problem. When I went to start my engine to get ready for my season I noticed the fresh water buzzer went off. This is when the problem started, I disconnected my hot water heater hoses thinking that there was a blockage in the line, so I by passed the hot water heater this did not correct the problem of the buzzing. Next I removed the fresh water pump thinking that the rubber impeller was defective, but when I looked this pump had a metal impeller so I reinstalled it. Next I removed my raw water pump and checked the rubber impeller and this looked good. What I will try to do is let my engine warm up and then remove the thermastat and see if the water will flow to my heat exchange and correct the problem. Anybody have a thoughts or insights that I maybe have missed.
Anthony:
That is why I asked about "Have you drained your coolant? Possible air in the cooling system." This is a common problem.
Whoever changed out the heater should know how to purge the system.
That is why I asked about "Have you drained your coolant? Possible air in the cooling system." This is a common problem.
Whoever changed out the heater should know how to purge the system.
Overheating Yanmar
A couple of weeks ago my 3GM30F overheated for an unknown reason. I limped in to home port after I let it cool and later replaced the thermostat with a 71 degree c replacement. It has not overheated since. I also added a mechanical guage to my engine on the outlet side of the water pump going to the water heater. I can now tell if my engine is "going" to overheat instead of waiting for the buzzer to go off by then it will be to late. I believe i experienced a fluke situation and the thermostat stuck in a closed position.
A couple of weeks ago my 3GM30F overheated for an unknown reason. I limped in to home port after I let it cool and later replaced the thermostat with a 71 degree c replacement. It has not overheated since. I also added a mechanical guage to my engine on the outlet side of the water pump going to the water heater. I can now tell if my engine is "going" to overheat instead of waiting for the buzzer to go off by then it will be to late. I believe i experienced a fluke situation and the thermostat stuck in a closed position.
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