Our '87 Hunter 31 Yanmar 2GM20 with about 700 total hours has recently developed a fresh water leak which in turn has caused the engine overheat alarm to come on several times in the past few weeks. After topping off the engine fresh water, including the expansion tank, it only takes a couple of hours before half the water ends up in the bilge and subsequently discharged overboard even with the engine shut down. I've have reached the point where I need a third opinion. So far we've installed a new mixing elbow, checked the thermostat, the raw water impeller, the raw water strainer, the heat exchanger, etc., so we're convinced there's no problem with the engine "plumbing". The oil looks good, as does the exhaust so we believe that the head gasket in okay. We've also checked the water heater for external leaks and none were found. Has anyone had a similar experience? If so I'd appreciate you input. Many thanks.
Engine Fresh Water Leak
- Thread starter Dave Winiker
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Some parts had nothing to do with fresh water leak
Some of the items you replaced had nothing to do with fresh water leaking into the bilge. Items such as mixing elbow, raw was impeller, strainer, exhust, etc. But it may be time for checking or replacing them anyway. Did you check all the hose fitting clamps? or the bleeder vent valve? To make sure all of them are tight and no leaks? How about the gaskets on the engine's plumbing system? Since it only take a couple of hours to drain a good amount of water, here's one way to find the leak. make sure the engine bilge is totally dry, or as dry as possible. Then place a large butcher paper or large piece of cloth below the engine, and make sure they are not going to touch the engine. Use duct tape to tape it down. Run the engine for a while with the engine box open. If there are any drips within the engine compartment, you should be able to spot the location right a way. If not, you can start looking elsewhere for the leak.
Some of the items you replaced had nothing to do with fresh water leaking into the bilge. Items such as mixing elbow, raw was impeller, strainer, exhust, etc. But it may be time for checking or replacing them anyway. Did you check all the hose fitting clamps? or the bleeder vent valve? To make sure all of them are tight and no leaks? How about the gaskets on the engine's plumbing system? Since it only take a couple of hours to drain a good amount of water, here's one way to find the leak. make sure the engine bilge is totally dry, or as dry as possible. Then place a large butcher paper or large piece of cloth below the engine, and make sure they are not going to touch the engine. Use duct tape to tape it down. Run the engine for a while with the engine box open. If there are any drips within the engine compartment, you should be able to spot the location right a way. If not, you can start looking elsewhere for the leak.
Question
Dave, You say the cooling water is discharged overboard. There should be no connection between the tray under the engine and the bilge. This is so that oily water cannot be accidentally discharged overboard. Are you sure the water going overboard actually comes from the engine? It seems possible that a bad head gasket is leaking cooling water into the engine where it goes down the exhaust. Alternatively there may be a connection between the fresh water and the raw water cooling circuits - possibly via a leak in the heat exchanger. Hope this gives you a lead.
Dave, You say the cooling water is discharged overboard. There should be no connection between the tray under the engine and the bilge. This is so that oily water cannot be accidentally discharged overboard. Are you sure the water going overboard actually comes from the engine? It seems possible that a bad head gasket is leaking cooling water into the engine where it goes down the exhaust. Alternatively there may be a connection between the fresh water and the raw water cooling circuits - possibly via a leak in the heat exchanger. Hope this gives you a lead.
Are you using antifreeze or plain water ?
Your Yanmar fresh water system (FWC) is made to use antifreeze, which does several things, one of which being the possibility of rising the operating temperature. Your post sound like you are using just plain water. If you were using antifreeze, a blown gasket would give you a sweet smelling odor. If leaking in the bilge, your bilge water would also show a slight film (or sheen) from the antifreeze. If the heat exchanger inside the hot water tank was leaking internally, the water coming out of the faucets would also have that feeling. Suggest you go rent a automotive rad pressure tester, remove the rad cap (it could simply be that creating the problem), and pressurize the system. I believe 13-15 pounds is the norm. If there is a leak somewhere, the pressure will drop steadily. You can easily identify if caused by the hot water tank by removing the 2 hoses from the inlet and outlet near the thermostat housing (see photo )and installing a short one to bypass the system. If pressure is steady after that, your problem is either with the hoses to the hot water tank or the heat exchanger in the tank itself. Your boat being an 87, my bet is the hoses are chafed somewhere, creating your leak. Good luck & Keep us posted
Your Yanmar fresh water system (FWC) is made to use antifreeze, which does several things, one of which being the possibility of rising the operating temperature. Your post sound like you are using just plain water. If you were using antifreeze, a blown gasket would give you a sweet smelling odor. If leaking in the bilge, your bilge water would also show a slight film (or sheen) from the antifreeze. If the heat exchanger inside the hot water tank was leaking internally, the water coming out of the faucets would also have that feeling. Suggest you go rent a automotive rad pressure tester, remove the rad cap (it could simply be that creating the problem), and pressurize the system. I believe 13-15 pounds is the norm. If there is a leak somewhere, the pressure will drop steadily. You can easily identify if caused by the hot water tank by removing the 2 hoses from the inlet and outlet near the thermostat housing (see photo )and installing a short one to bypass the system. If pressure is steady after that, your problem is either with the hoses to the hot water tank or the heat exchanger in the tank itself. Your boat being an 87, my bet is the hoses are chafed somewhere, creating your leak. Good luck & Keep us posted
Maybe it is your fresh water system,
Are you sure it is not your fresh water tank or hoses that are leaking and not the engine? In our 1984 Hunter 30. we found a crack in the fresh water fill hose that was allowing water to make its way into the bilge and setting off the pump on a regular basis. The crack in the hose was buried under the cockpit sole. Look in the aft compartment under the quarter birth. Another option is a food dye in your fresh water tank.
Are you sure it is not your fresh water tank or hoses that are leaking and not the engine? In our 1984 Hunter 30. we found a crack in the fresh water fill hose that was allowing water to make its way into the bilge and setting off the pump on a regular basis. The crack in the hose was buried under the cockpit sole. Look in the aft compartment under the quarter birth. Another option is a food dye in your fresh water tank.
Fresh Water Leak ;D
EUREKA!! "We" (me, myself and I) found the leak - with your help of course. After almost $1,000 in labor and parts I found that the engine fresh water hose which connects to the hot water heater had sprung a leak at the hose clamp where it connects to the hot water heater hose. Yesterday, after bypassing the hot water heater circuit, we took "Champagne on Ice" for a 2 hour motor and all was AOK. The reason we didn't find the leak initially was because this connection was out of sight inside the opening between the engine and the water heater compartments. This explains why the fresh water was finding its way into the bilge. I want to thank all of you who responded to my original post. In hindsight it was a BGO (Blinding Glimpse of the Obvious) as to where the leak was occuring. Now its time to drain the system, add antifreeze and get ready for winter. Fortunately winter in SE Virginia is usually quite kind to us and we're bound to be a few good sailing days between now and the new year. Happy Thanksgiving. Dave Winiker
EUREKA!! "We" (me, myself and I) found the leak - with your help of course. After almost $1,000 in labor and parts I found that the engine fresh water hose which connects to the hot water heater had sprung a leak at the hose clamp where it connects to the hot water heater hose. Yesterday, after bypassing the hot water heater circuit, we took "Champagne on Ice" for a 2 hour motor and all was AOK. The reason we didn't find the leak initially was because this connection was out of sight inside the opening between the engine and the water heater compartments. This explains why the fresh water was finding its way into the bilge. I want to thank all of you who responded to my original post. In hindsight it was a BGO (Blinding Glimpse of the Obvious) as to where the leak was occuring. Now its time to drain the system, add antifreeze and get ready for winter. Fortunately winter in SE Virginia is usually quite kind to us and we're bound to be a few good sailing days between now and the new year. Happy Thanksgiving. Dave Winiker
Brings back memories...
This reminds me of our experience a couple years ago diagnosing an overheating problem. We spent 4 or 5 hours checking out every part of the cooling system and couldn't find the problem. My partner solved it when he discovered that the water pump belt was worn to the point that it wasn't running in the pulley properly, thereby not driving the water pump. From then on we learned to check the simplest things first when diagnosing a problem. At least we didn't spend three boat units, only an afternoon when we could have been sailing.
This reminds me of our experience a couple years ago diagnosing an overheating problem. We spent 4 or 5 hours checking out every part of the cooling system and couldn't find the problem. My partner solved it when he discovered that the water pump belt was worn to the point that it wasn't running in the pulley properly, thereby not driving the water pump. From then on we learned to check the simplest things first when diagnosing a problem. At least we didn't spend three boat units, only an afternoon when we could have been sailing.
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