Farryman/Paguro generator - water pump problem

[kashurst]

Having a problem with the generator raw water pump on my new to me boat. When I tested it a few weeks ago it all worked fine except cooling water flow was virtually non existant. Obviously a dead impeller or a blockage somewhere.....
Put a new one (maybe it isn't new after all) in today and no improvement to water flow
so I pull the hoses off either side of the water pump and put on a @ 1m of plastic pipe on each end and both ends into a bucket of water to test the pump and verify which side is the inlet, which is the outlet.
start the gennie (only on long enough to do the test)
water flows but hardly any pressure, I can stop the flow really really easily by pressing my thumb on the end
also I checked the direction of rotation and I think the pump is upside down - or my gennie is running backwards?
I don't think that's possible on a 4 stroke is it?
Flexible impeller pumps take the liquid the long way around don't they?
what is my obvious error???? thanks

 

[Portofino]

Pump will be a Johnson derivative ?
Unlikely due to mounts to be fitted upside down, or wrong way round .
The seal on the spindle may be worn letting in air -loosing suction ? Any evidence of leak when standstill ?
Face inside the cover plate -a gap between rubber impeller vanes - unable to draw enough loosing pressure .

Assuming pump is ok ??

Does the water run through the windings ? If so they fur up if Al ? Restricting flow

Or has the spray pipe on the exhaust manifold corroded restricting flow -- does it feel cool down stream should be able to keep your hand onit .Obviously hot above the water inlet point .

 

[kashurst]

it is a johnson pump
however it is possible to release two clamps and rotate the pump body 360 degrees. I am only testing the pump at the moment without it being plumbed into the gennie.
however I have examined the rest of the circuit and I can blow into it and water comes out the other end very easily. The gennie is 14 years old but only shows 8 hours of use so I am wondering if it has ever worked properly.

 

[superheat6k]

I would not rule out fouled rate passages. When I had the head of mine due to valve problem the water channels were heavily crudded up with salt. The head is simple to remove, just make a note of which push rod sits in which position as they can easily be muddled up.

I have the Farymann manuals so PM me if you would like them.

 

[KevB]

I've recently fitted a johnson pump to a genny and the pump had direction arrows cast into the body.

maybe the pipes are on the wrong way?

 

[kashurst]

problem solved - the pump has been run dry a few times and the inside surface of the pump is coated in rubber. I cleaned it all out and polished the surfaces with wet & dry sandpaper to get back to shiny brass/bronze. Pump works great. The pipes/pump were the correct way around.

 

[jimmy_the_builder]

Well done. But then again, we shouldn't be surprised - wasn't it you that basically rebuilt a D9 in your last boat?

 

[petem]

Well done. But then again, we shouldn't be surprised - wasn't it you that basically rebuilt a D9 in your last boat?

I think it was the gearbox, but still proper man skills!

 

[kashurst]

er yes that was me, sucker for punishment, very happy with my KAMD 300s on the new toy , love those superchargers. woosh and we are off!