75 4 hp Johnson water pump

[PW2]

I have a 1975 4hp that seems to have a small split in the water pump housing. The parts store only lists replacement impellers and plates. It doesn't appear to go all the way thru the housing, but it juts out a bit on the inside where the impeller rides, and it is clearly noticeable by feel.

It wasn't cooling, and while the impeller that came out is clearly worn some, it looks like it should have pumped water. The motor is new to me, and I have not had the head off yet to check if all water passages are free of debris.

Any suggestions on whether the pump housing could be the culprit ( My guess is that while it maybe should be replaced, as well as the impeller, there is some other reason why it isn't circulating water and cooling) or something further needs to be checked?

 

[F_R]

Re: 75 4 hp Johnson water pump

You can rig up some way of running water up through the water tube to see if it goes all the way through, for whatever it's worth.

The water pump housing is part number 310344, from a dealer. Or for the better deal, part number 379770 gets a complete kit, including impeller, plate, housing, screws and grommet.

These assume you have the weedless drive. The right angle drive has no pump housing, you have to replace the whole gearcase on that one.

 

[PW2]

Re: 75 4 hp Johnson water pump

Yep, I have the weedless, and the pump housing is sitting right here on my desk. Thanks.

Assuming the water goes thru the water intake tube ok per your test, does that pretty well assure me that the water jackets are all clear? There was a bit of sand or something in and around the pump housing--but not seriously caked or anything.