I have an 1981 Hunter 30 that always starts well when the engine is cold. However when the motor is hot I get the idiot light that it is overheating and not pumping water. By the time a service man checks the boat over it is pumping fine. It only does this when it is starting never while running. It was suggested that I may be draining my water line and getting air into the impeller. A mechanic told me to start the engine at close to full throttle to generate as much initial vacuum as possible then throttle down after the motor starts. Any advice appreciated.
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Ken Keitges
Over temperature Indicator
If your sure that that the water is in fact not over heating it may be that replacing the temperature sensor would fix the over temperature indicator problem.
If your sure that that the water is in fact not over heating it may be that replacing the temperature sensor would fix the over temperature indicator problem.
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Paul Akers
Watch for steam
You didn't say if you had raw water cooling or sealed fresh water cooling. I'll assume fresh water cooling. When the warning light comes on, check the exhaust to see if it's blowing any white steam. This is a definite sign of overheat. Then, after you shut it down, feel the black hoses that run off of the water pump. They should be hot. If they are cold, that means that the thermostat is still closed. If that's the case, it may be a thermostat problem. As the engine heats up, the thermostat should open and pass out the hot water to let cool water in.
You didn't say if you had raw water cooling or sealed fresh water cooling. I'll assume fresh water cooling. When the warning light comes on, check the exhaust to see if it's blowing any white steam. This is a definite sign of overheat. Then, after you shut it down, feel the black hoses that run off of the water pump. They should be hot. If they are cold, that means that the thermostat is still closed. If that's the case, it may be a thermostat problem. As the engine heats up, the thermostat should open and pass out the hot water to let cool water in.
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Steve T.
yanmar over heating
Make sure that your fresh water intake is clear of debris. I had this problem about a month ago. I took a garden hose and forced water back through the thru-hull and cleared debris. I confirmed I had good water flow by the stream of water about 4" high. That solved it for me. Steve
Make sure that your fresh water intake is clear of debris. I had this problem about a month ago. I took a garden hose and forced water back through the thru-hull and cleared debris. I confirmed I had good water flow by the stream of water about 4" high. That solved it for me. Steve
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Tom
Check heat exchanger
We had this problem a couple of years ago, and it turned out to be the heat exchanger. The tubes had sufficient mineral deposits to cause overheating at higher rpm's. We had it cleaned by the yard, but it's an easy do it yourself job.
We had this problem a couple of years ago, and it turned out to be the heat exchanger. The tubes had sufficient mineral deposits to cause overheating at higher rpm's. We had it cleaned by the yard, but it's an easy do it yourself job.
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Randy Williams
Question on cooling water flow.
Just moved onto an 88 Hunter 30 in the Clear Lake, TX area. What is the normal flow of cooling water that should be comming out of the exaust with the stock 2 cyl yanmar 2GM20F. mine blurps out a little water at about 10 second intervals. Enging seems to run ok but seems like flow should be more -could raw cooling water impeller be installed with tips in the wrong direction? Randy Williams s/v CABARET WB5CNM
Just moved onto an 88 Hunter 30 in the Clear Lake, TX area. What is the normal flow of cooling water that should be comming out of the exaust with the stock 2 cyl yanmar 2GM20F. mine blurps out a little water at about 10 second intervals. Enging seems to run ok but seems like flow should be more -could raw cooling water impeller be installed with tips in the wrong direction? Randy Williams s/v CABARET WB5CNM
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Bob E.
Cooling water flow
A blurp every 10 seconds does sound like not enough flow. Mine blurps about ever 3 seconds or so.
A blurp every 10 seconds does sound like not enough flow. Mine blurps about ever 3 seconds or so.
All of these things & don't forget....
The raw water exits the boat through the mixing elbow. These can cause numerous problems. It is not difficult to remove them. Four bolts on the back of the head on a 2gm/3gm and then trying to remove the exhaust hose is probably the most difficult. The elbow can be cleaned but it is recommended that you purchase a new one (about $100). When you replace the elbow a new exhaust gasket is in order.
The raw water exits the boat through the mixing elbow. These can cause numerous problems. It is not difficult to remove them. Four bolts on the back of the head on a 2gm/3gm and then trying to remove the exhaust hose is probably the most difficult. The elbow can be cleaned but it is recommended that you purchase a new one (about $100). When you replace the elbow a new exhaust gasket is in order.
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Terry Arnold
overheating indication when starting hot?
An overheataing signal when starting up when hot may be an indication of not having shut the engine down according to the manual. I believe that it says to run it at idle for several minutes before cutting it off. Otherwise, the temperature of the stagnant water inside the engine (including the water at the sensor) will rise after cut off above the limit.
An overheataing signal when starting up when hot may be an indication of not having shut the engine down according to the manual. I believe that it says to run it at idle for several minutes before cutting it off. Otherwise, the temperature of the stagnant water inside the engine (including the water at the sensor) will rise after cut off above the limit.
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