I have a 1981 Hunter sailboat w/Yanmar 1GM diesel. After it idles for 2-3 minutes, the temp light comes on. I have checked the impeller and it appears to be OK. Water expulsion from the boat appears to be OK and the hoses from the engine are only warm to the touch not hot. Anyone have any thoughts as to what the problem might be. I have tried to have mechanics out but no one seems to want to work anymore. All I get is excuses as to why they can't come out. Going on 5 weeks now. Thanks
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try this
Take the water hose that goes into the exaust elbow off, make sure it is not at all obstructed, this passage must be kept open to get proper flow. It may look ok but you get tricked by the gradual decline in water flow. id try it next.
Take the water hose that goes into the exaust elbow off, make sure it is not at all obstructed, this passage must be kept open to get proper flow. It may look ok but you get tricked by the gradual decline in water flow. id try it next.
Boat mechanics soon learn that it does not pay
to work on (1) old, (2) small (3) sailboats. Add to that the the boat is on a (4) lake and I'm surprised they just don't hang up the phone on you. Old small boats and their owners are generally bad news for mechanics. Diagnosis is often complicated by a myriad of worn out components. Disassembly and installation are further complicated by rusted or busted nuts and bolts. The chances of them breaking something while trying to perform a fix escalate exponentially. The owners tend not to understand that the repair for their old boat is not based on a percentage of the boats value but that it will cost just as as much as it would for a new boat. Mechanics are usually asked to perform an inexpensive fix which the boat owner will expect him to guarantee forever. They rather work in a large new boat with air conditioning and an owner that tells them to go ahead and replace this and that as suggested and put it on his bill. If you think I'm exagerating call the same mechanics back and tell them you need some work on your 40' Hatteras docked at the fanciest marina in your area and see how soon their schedule opens up. Then fix the boat yourself. The cooling system of a 1GM is quite simple. Hunter used seawater cooling on their Cherubini 27's. Check the raw water inlet clam for any obstruction. Check the impeller, remove the hoses and clean the insides or replace. If the hoses and passages were clear and free of debri then remove and test the thermostat. Place a pot of water on the stove and get a cooking thermometer. Suspend the thermostat on a piece of wire and immerse in the water. turn the stove on and record the temperature where it starts to open it should be close to the temperature stamped on the thermostat. Continue to heat the water up another 25 degrees F and by now the thermostat should be fully open. If the thermostat has not started to open at the stamped temperature and is not fully open at +25 degrees then replace. Let it cool to 10 dgrees below the stamped opening temperature and it should be closed if not replace. A last visual check should confirm a tight seal when closed. The next thing to check is the temperature sensor. I should be color coded white with a closed temperature of 148-154 degrees F. To test use the kitchen thermometer and a container of oil and an ohm meter. Connect the ohm meter on the leads and immerse the switch and heat the oil; it should close at 148-154 degrees. Then let it seat and cool down and it should open at no cooler than 136 degrees. The ohm meter will let you know when is it closed or open. Check wiring harness for a short. If you have good water circulation from seacock to exaust and the thermostat and switch are working to specs and there is no electrical short in the iring and the engine is still overheating then we have an internal engine problem. Good luck.
to work on (1) old, (2) small (3) sailboats. Add to that the the boat is on a (4) lake and I'm surprised they just don't hang up the phone on you. Old small boats and their owners are generally bad news for mechanics. Diagnosis is often complicated by a myriad of worn out components. Disassembly and installation are further complicated by rusted or busted nuts and bolts. The chances of them breaking something while trying to perform a fix escalate exponentially. The owners tend not to understand that the repair for their old boat is not based on a percentage of the boats value but that it will cost just as as much as it would for a new boat. Mechanics are usually asked to perform an inexpensive fix which the boat owner will expect him to guarantee forever. They rather work in a large new boat with air conditioning and an owner that tells them to go ahead and replace this and that as suggested and put it on his bill. If you think I'm exagerating call the same mechanics back and tell them you need some work on your 40' Hatteras docked at the fanciest marina in your area and see how soon their schedule opens up. Then fix the boat yourself. The cooling system of a 1GM is quite simple. Hunter used seawater cooling on their Cherubini 27's. Check the raw water inlet clam for any obstruction. Check the impeller, remove the hoses and clean the insides or replace. If the hoses and passages were clear and free of debri then remove and test the thermostat. Place a pot of water on the stove and get a cooking thermometer. Suspend the thermostat on a piece of wire and immerse in the water. turn the stove on and record the temperature where it starts to open it should be close to the temperature stamped on the thermostat. Continue to heat the water up another 25 degrees F and by now the thermostat should be fully open. If the thermostat has not started to open at the stamped temperature and is not fully open at +25 degrees then replace. Let it cool to 10 dgrees below the stamped opening temperature and it should be closed if not replace. A last visual check should confirm a tight seal when closed. The next thing to check is the temperature sensor. I should be color coded white with a closed temperature of 148-154 degrees F. To test use the kitchen thermometer and a container of oil and an ohm meter. Connect the ohm meter on the leads and immerse the switch and heat the oil; it should close at 148-154 degrees. Then let it seat and cool down and it should open at no cooler than 136 degrees. The ohm meter will let you know when is it closed or open. Check wiring harness for a short. If you have good water circulation from seacock to exaust and the thermostat and switch are working to specs and there is no electrical short in the iring and the engine is still overheating then we have an internal engine problem. Good luck.
Thanks for the help
Thanks guys for the ideas. I am going down to the boat Thursday and I will do the tests that you suggest. Wish me luck. By the way, what suggestions do you have to reach the top inside screw on the impeller housing?
Thanks guys for the ideas. I am going down to the boat Thursday and I will do the tests that you suggest. Wish me luck. By the way, what suggestions do you have to reach the top inside screw on the impeller housing?
Line up the
the hole in the flywheel and you can sort up reach it or use one of those 90 degree screw drivers. I replaced mine with a thumbscrew after I finally got it out. Also it is real easy to just remove the entire water pump and then service the impeller. I have had overheating problems for 3 years. Two expert mechanices later and it turned out to be a blown head gasket and a bad valve. When the head was off we found crap clogging the woter ports and reamed them out. Now I'm selling the boat go figure.
the hole in the flywheel and you can sort up reach it or use one of those 90 degree screw drivers. I replaced mine with a thumbscrew after I finally got it out. Also it is real easy to just remove the entire water pump and then service the impeller. I have had overheating problems for 3 years. Two expert mechanices later and it turned out to be a blown head gasket and a bad valve. When the head was off we found crap clogging the woter ports and reamed them out. Now I'm selling the boat go figure.
Got er Done
Thanks guys, I started at the seacock and worked my way thru the lines to check for blockages to no avail however, The T-fitting that screws into the block just before the thermostat and after the impellar was the culprit. I found 2 pieces of an old impellar lodged in the fitting just before going into the block. After I removed them and fired it up. Wham no more red lights and she runs great. Thanks for all your help. I am going to have to replace the seacock and thermostat as a precaution and I did put in a new impellar.
Thanks guys, I started at the seacock and worked my way thru the lines to check for blockages to no avail however, The T-fitting that screws into the block just before the thermostat and after the impellar was the culprit. I found 2 pieces of an old impellar lodged in the fitting just before going into the block. After I removed them and fired it up. Wham no more red lights and she runs great. Thanks for all your help. I am going to have to replace the seacock and thermostat as a precaution and I did put in a new impellar.
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