Ever Hear of 'Air-Lock' Trouble In Raw Water Circuit (Yanmar 2gm) ?

[brantleychuck]

A friend of mine had that same problem for years. Lots of talk about " Air Locks" After 3 years of having a unreliable engine he replaced the pump and the problem has gone, Just replace it.

[EveningTide]

I had problems with air locks that were cured when I replaced the water pump">raw water pump. That was two year ago and guess what? The new pump has started to develop the same symptoms as the first pump. Twice in the last month I have had to rev the motor to get water flowing. If this progresses like the first pump, by next year revving will not be enough and only bleeding out the air will work. Only closing the water inlet to the motor while sailing kept the problem from occuring once the original pump was several years old. (Maybe I should just always sail without heeling more than 20 degrees. Then air won't enter the inlet line.)

[sartorst]

Some years ago my friend and I relocated his strainer to an easier to get location ! NO problems before or after until months later when sailing offshore in some rough conditions the engine would air lock and overheat we were glad the strainer was easy to get to until we realized each big wave a really small gulp of air would be sucked into the strainer which no longer had a steady upward climb to the pump and would build to the point of loosing prime the short term repair was to remove it from its higher mounted position and lay it lower in the bilge this is where it remained with no more problems until relocated back to the more difficult location

[EveningTide]

Thanks Sartorst- My strainer is at the high point of the input line with the pump more than one foot lower. To get the air out I lift the lid on the strainer for a few seconds until water overflows, then the pump works fine. I will have to look at how the inlet hose is routed to be sure there aren't any other high spots that could collect air. Only once in 11 years have I had the pump air lock while motoring and now I am careful to limit heel angle when motor-sailing. The usual problem is heeling while sailing, getting air in the line and then air lock when the motor is next started. I can always tell by exhaust sound when there is no water flowing and it has never gotten to the point of overheating.

[delmarrey]

You might want to check all you hose fittings to see if they're tight. They could be sucking air into the system, especially of your getting growth in your thruhull fitting. As well, the strainer could be sucking in air.

I've alway made it a habit to install one size up for thruhulls vs the pump inlet size.

[Northeaster]

Sorry to revive an old thread, but as it's only 9 months ago, maybe others are still battling this issue.
I thought I posted this earlier - but I turned the water pump cover to the opposite side, aftre cleaning the paint from it - can do this o some models and this cured the issue.
The over was worn slightly and I am pretty sure the resulting slight loss of effciency was enough that it could not overcome some operating conditions. Has been great ever since.

[svstrider]

[QUOTE=bill good;172472 Get a service manual if you intend to do your own work as every thing is covered & the internals are better understood. (The impeller has a repution of becomming unbonded from the shaft in the 1GM pumps but I do not know if it is a problem on the 2GM.)
regards Bill Goodward[/QUOTE]
I have a 3GM30 andhave 3 impellers unbond from the shaft in the last 2 years. Poor manufacturing by the bloody chinese as usual. Air locks can be in the exhaust manifold. I have a raw water cooled Yanmar. Close off the raw water inlet. Filll back from there. Also take off the hose to the exhaust mainfold and fill that with a funnel. Start engine and once it is going open raw water inlet on sail drive. Works for me when I have changed the water pump and it is not pumping water.

[Patrick_123]

I have a yanmar Diesel 2gm20 sea water cooled.
The engine has being going perfect till one day it became difficult to start. I discovered water dripping from the air inlet. The engine did start after a while & seemed to run okay. The water is still slowly dripping? Has anyone ever come across this before or know how to fix it?

Thanks for your advice & safe fishing!