40e74s 1974 40hp - not pumping water

[gumblebop]

Hi, I have taken the water pump apart on my Johnson, the impeller appears to be fine, however it is not putting any water out the water outlet half way up the outboard, I have been told there is no thermostat on this model, is there anything else I can check?

Many thanks

[Joe Reeves]

When removed from the impeller housing the impeller blades should spring out straight from the curved appearance they have when installed. If the blade still retain that curved appearance.... replace it.

If running on a flushette, the water must be turned on full blast, otherwise the water pump will possibly draw air.

If running in a tank, large trash can, whatever... the water level must be 4 or 5 inches above where the lower unit bolts up to the long exhaust housing so as to have the water pump submerged, otherwise the water pump will most definitely draw air.... it is not a self priming pump!

If all of the above is as it should be and there is still a no pumping situation... check the engine's compression as a head gasket problem will allow the combustion to enter the water passages which will result in a stalemate... combustion going down, water coming up, neither going anywhere!

[gumblebop]

Many thanks for your response JR.............

I am sure the water inlet is deep enough in the water - perhaps I should try it a little lower.

The only other thing I can think of is that the impeller key appears to be binded to the impeller - meaning the impeller is fixed in place to the drive shaft. Would this affect the pumping ability of the impeller ?


Many thanks again

[Joe Reeves]

The impeller binding (sticking) to the driveshaft would indicate that it's been on there for quite some time. To answer your question.... if a impeller in perfect condition was stuck on the driveshaft, I would a$$ume that it stuck while in the proper location.

If that impeller has been on the engine for a few years (or more), I'd change it.

Frankly I never bothered with just the impeller... I changed the entire water pump a$$embly to avoid possible double work.