Yanmar 1GM10 water pump problem

[jsvba]

Got a virtually brand new, 2 year old, less than 75 hours, 1gm10 and I replaced the impeller when I winterized it last fall because it wasn't pumping quite enough raw water towards the end of the year.

Started her up, recently, ran fine and pumped the normal amount of raw water through the exhaust for 20 minutes or so, but as soon as I kicked the rpms up to 2000 it stopped pumping any water at all.

I have my suspicions but would love to hear what anyone else thinks might be the real problem here.

Thanks in advance
Mike

 

[Benny]

The blades portion of the part may have separated from the metal drive bushing. Only way to know is to open the pump and check the impeller. Don't forget to check for possible obstruction specially if you do not run a strainer at the intake hose. An obstruction can act as a flap valve disrupting flow. I don't think a malfuctioning thermostat would react to RPM increase but if everything else checks out check it out for closing and opening at it's temperature range.

 

[Stu Jackson]

1. If engine driven (i.e., not belt driven) the blades may have separated from the shaft.

2. If belt driven, same as #1, PLUS the belt may be slipping.

3. You may have an obstruction in the line or the through hull may be blocked.

That's what I'd look for if it was my boat.

Interesting question, hope you're successful in your detective work and will let us know if you caught the varmint.

 

[sailingdog]

Or the blades on the impeller could have come off the hub. This happens on impellers that have aged or been run dry and become brittle.

 

[Sailm8]

I went through this only mine was an overheating problem. Check the raw water intake under the boat. Here in FL mine had a bunch of clams or something living up the intake. Cleaned those out. Next I found out there were a bunch of bad impellers in the yanmar stock. Like the poster above said the center metal hub would spin and slip under load. I replaced that no fix. Next I replaced all of the hoses and the temostat. No fix but could have been. I pretested the thermostat in a pan of hot water . It was good but did not fix the problem. Next was the exhaust elbow. Took it off and it has a little soot but no obstruction. Replaced the injector because someone said it might be running hot if I had a bad injector. No fix. Finally I called two mechanics. The first did some razzel dazzel for $160 but no fix. The last mechanic found a blown head gasket and this fixed the problem.

On my 1gm it is really hard to tell how much water it is moving. It sort of comes out in spurts and not a steady stream. It no longer overheats so I am pleased. Hope some of this helps. My motor was in salt and is over 25 years old but still runs great. (When it wasn't overheating)