Raw Water Pump Problem

[Joe Mullee]

I have a 1983 H34 with a Yanmar 3GMF. I'm not getting water out the exhaust. I checked the thru hull and it's not obstructed. I checked all hoses to the raw water pump and they're OK. The strainer is OK. It doesn't appear there's water coming out the pump. I replaced the impeller. The hose at the heat exchanger is relatively dry. The hose at the output side of the heat exchanger is totaly dry. The way I first noticed there was no water out the exhaust was the buzzer at the control panel was going off. I had been in the enclosed cabin and don't know how long the problem existed. At the time the buzzer was heard the engine had been running 90 minutes in very cold conditions (30F outside). The engine never overheated and has started right up since.Could the raw water pump have been damaged? Maybe burned out somehow? I need help with some ideas as to why there's no water coming out.Thanks.Cou

 

[Ed Schenck]

Pump problem isolation.

It should be relatively easy to prove/disprove the pump as the problem. Attach a piece of hose to the inlet side of the pump and put it in a bucket of water. Attach another hose to the outlet side and route it to the same bucket. Have someone start the engine while you hold the hoses. You should see a a fair amount of water flowing out of and back into the bucket.If the pump is OK then reattach the inlet hose. Keep the outlet hose in the bucket and try again. If this flow is good then there is blockage in the heat exchanger or hose leading to it. If you keep these tests to a minute or less you won't hurt the Yanmar.

 

[Eric Swift]

Hi Joe!

I notice on the other posting that someone had a blockage in the hose leading from the thru hull to the strainer. But I think the last posting is right, you need to isolate the pump and make sure it is working. That smoking might have indicated some damage there. I would agree that going step by step to see if the pump works by having a hose from a bucket of water pumped back into the bucket. If the pump works, work forward by adding the hose to the exchanger, to the elbow etc. step by step. In the same way you can go back to add the strainer, the hose from the thru hull, and the thru hull. At some point it will work one way and not the other and you will have the solution. The pump is the first step though. Good luck.

 

[Patrick Neeley]

raw water intake

Another angle - take your hose off the sea cock and check that there is no obstruction there. It's not as likely in a sailboat because of the elevation of the inlet from the bottom, but in a friend's power boat after spending many dollars with a boat yard to replace the pump impeller, thermostat, boiling out heat exchanger, etc. he found it himself. A quarter sized seashell had "just" gotten through the sea cock and was lodged right above it in the hose. The shell blocked enough water flow to run the temp up on that engine when he ran above 2500 RPM. Obviously, he touched a shoal and sucked up that shell, and it didn't go all the way to his strainer.

 

[joe phibbs]

overheating-no water!

We had the same kind of problem with the 2GM20F on ALURE, a 31 Hunter. We finally realized whoever replaced the raw water intake to pump hose used an automotive type that collapsed when engine ran faster than 2000 rpm. That caused the engine to run hot and restricted water supply to engine. joe