Yanmar 3GMD Water Drains From Engine Under Sail

[tomgrigsby]

I have a Yanmar 3GMD, raw water cooled, and a siphon break around the exhaust elbow. When under sail, if I leave the raw water thru-hull open, it takes seemingly forever for the water to start coming out the exhaust after the motor is restarted. If I close the raw water valve after shutting down the engine, and then reopen it of course for startup - no problem. I suspect the water is siphoned out of the engine if I leave the inlet open under sail, and it just takes a while to refill the engine before I see water out the tailpipe. Is this normal, and/or, is this a problem? Appreciate any thoughts on the matter. Its a pain to go below to open the valve when I'm ready to restart.

 

[whatfiero]

There's nothing wrong as long as pump primes quickly and you keep an eye for water flow I would take a look at raw water pump thou because water should not be able to syphon past pump if your missing some fins or have worn edges on impeller then problems solved with impeller replacement

 

[NYSail]

Your siphone break needs to be above the water line and as center as possible. Otherwise you will have issues with water back flowing into your engine...... especially with the yanmar exhaust elbow.

 

[Benny17441]

It is not only a pain to go below before restart but will be more of a pain the first time you forget to open the valve. It should not be a problem as long as long as the overheat alarm does not go off. The overheat alarm is set to go off way before engine damaging heat builds up so there is a good cushion of time in which to turn the engine off. We have a temperature gauge and in one occasion our overheat alarm went off but we determined that the temperature was high but stable and since we were making our approach into an unfamiliar harbor and trying to beat the setting sunlight we motored on for another 30 minutes listening to the darn buzzer. After docking we removed a plastic bag that was partially blocking the intake and inspected the impeller and all was fine. Just make sure your temperature sensor and buzzer are working properly and trust them to do their job.

 

[tomgrigsby]

Your siphone break needs to be above the water line and as center as possible. Otherwise you will have issues with water back flowing into your engine...... especially with the yanmar exhaust elbow.

Siphon break is well above waterline. In fact, the exhaust elbow is close but probably above. Thanks

 

[tomgrigsby]

It is not only a pain to go below before restart but will be more of a pain the first time you forget to open the valve. It should not be a problem as long as long as the overheat alarm does not go off. The overheat alarm is set to go off way before engine damaging heat builds up so there is a good cushion of time in which to turn the engine off. We have a temperature gauge and in one occasion our overheat alarm went off but we determined that the temperature was high but stable and since we were making our approach into an unfamiliar harbor and trying to beat the setting sunlight we motored on for another 30 minutes listening to the darn buzzer. After docking we removed a plastic bag that was partially blocking the intake and inspected the impeller and all was fine. Just make sure your temperature sensor and buzzer are working properly and trust them to do their job.

Appreciate the input. Not sure I actually have and overheat alarm, but water flow starts in maybe 60 seconds, so, thanks!

 

[tomgrigsby]

yes that worries me too. Ready to forget. Appreciate the input. Not sure I actually have and overheat alarm, but water flow starts in maybe 60 seconds, so, thanks!

 

[Chris Patterson]

60 seconds, that IS a long time.


A test: Have someone else crank the engine while you put your hand on the cover of the sea water pump. With no water going through the pump, the cover will get very hot, very fast. You will know if water is getting pumped that far anyway..

Note. If this happens too many times, the impeller will be disintegrated in short order.

 

[tomgrigsby]

I take it most boats don't do this. I'm pull the impeller and check for missing vanes, and check for heat. Appreciate the help.

 

[Benny17441]

A short delay in seeing water out the exhaust does not necessarily mean the pump is running dry. Usually the pump is primed by water being pushed up the intake hose as the hull pushes down. It could mean that some water escaped from the engine or that the thermostat could be restricting the flow of water until the engine warms up . If there was no water in the pump the impeller would desintegrate before 60 seconds. That could be tested by disconnecting the output hose from the pump before cranking the engine to see if there is water flowing out. There should be an overheat alarm with a light and a buzzer in the control panel. There is a toggle switch in the panel to test the temperature alarm circuit. If the warning lamp does not come On and the Buzzer does not sound something is faulty and must be repaired.