6hp - water pump working fine, no blockage in engine but still not pumping water?

[Lenny25]

I have a 70'a model, Johnson 6HP seahorse. It stopped pumping water due to a blockage in the cooling system caused by sand and a small piece rubber that broke off the tip of one of the impeller blades. After clearing the obstruction, I connected my garden hose to the copper pipe coming from the water pump, and water flowed easily through the engine and came out the exhaust hole. I even took off the thermostat cover to check that water was flowing through there. Btw, I discovered the previous owner had removed the thermostat and not replaced it (a missing thermostat should not influence the water flow)

The next thing I did was to dissemble the water pump and inspect, every thing was good, the impeller was recently replaced, it was just the tip of one of the fins gone. I put it all together, and tested it in a bucket of water by spinning the drive shaft with my drill. It seems to pump water with no problems.

Then I reassembled the whole motor, taking extra care that the copper pipe was properly seated in the impeller housing (the top end of the pipe is securely stuck, I left it like that cos im not going to try fix something that aint broke. Started it up, but no water coming out the exhaust vent! I only let it run for a few seconds, cos I'm scared of over heating the motor. Any ideas what the reason could be that its not circulating water?

 

[emoney]

Re: 6hp - water pump working fine, no blockage in engine but still not pumping water?

Are you sure you had it submerged far enough in the water? I had the 6hp in an 80's version and if you didn't get it into water well over where the lower unit attaches it wouldn't pump.

 

[nwcove]

Re: 6hp - water pump working fine, no blockage in engine but still not pumping water?

am i reading this right? you put the impeller back in, because it was recently replaced.....and just the tip of one of the vanes was gone?

 

[Lenny25]

Re: 6hp - water pump working fine, no blockage in engine but still not pumping water?

that's right, i put the same impeller back.

I did discover the water depth thing, when testing the impeller with the drill, the water level needs to be higher than the impeller housing in order for it to fill with water.

I just don't get it, its a real mystery to me, cos all the right things are working seperately, but bolt the bottom end back on, and it doesn't work... I'm quite stumped

 

[nwcove]

Re: 6hp - water pump working fine, no blockage in engine but still not pumping water?

you need to replace that impeller, and inspect the impeller housing/plate. either replace or reseal the gaskets . the pump has to push water up about 3ft through some restrictions, try blowing through a small hose with three feet of water in it above you.....not easy! also have a look at the intake screen.