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sanuni 01-29-2002 04:45 PM

Cooling pump blues
I''m having trouble with my Newport 27''s raw water pump which is causing the diesel engine to overheat. After looking for an obstruction in either the intake or exhaust side, including the heat exchanger, I found nothing. The flexible impeller spins with the motor and appears to be in good shape. Any suggestions?

OzBeowulf 01-30-2002 01:57 AM

Cooling pump blues
You didn''t mention the thermostat. Have you removed and test it? And what about calcification in hoses, etc? Is the water flow at the exhaust flow normal or diminished?

Also, just a thought, but are you absolutely sure the rubber impeller is firmly bonded to the bronze inner core?

I''m thinking that you''ve seen the impeller go around with the pump''s cover plate off, but the drag on the end plate is slowing or stopping impeller rotation in actual use. This was a real problem for many GM series Yanmars a few years back.

Otherwise, it''s hard to tell. What brand diesel? Have you cleaned the heat exchanger or just eyeballed one or both ends?

Good luck,


sanuni 01-30-2002 03:10 AM

Cooling pump blues
I have a Universal Diesel; I believe 14 hp with a heat exchanger. I have not checked the thermostat, as it “appears” to be the raw water pump. The flexible impellor pump only produces a flow if the pressure side is held below the water level and even then it has VERY little pressure.

I’m not sure if the flow volume is diminished; it trickles (when held below water level) with the engine off, but “flows” well enough through the heat exchanger to keep the engine cool while running as long as the hose is NOT connected to the engine exhaust (or held above the water line).

Water flows freely, when blown or sucked, through both the intake AND the discharge at the pump. And the light flow appears to be the same before and after the heat exchanger.

Yes, it spins with the cover off and the impellor appears to be well seated in the shaft (which is directly geared into the engine…no belts).

Please don’t take anything I’ve said as final as I realize that if everything IS as it APPEARS this pump would be working great :-). Any suggestions are appreciated.

bobneidhardt 01-30-2002 11:21 AM

Cooling pump blues

Change the impeller ! If it doesn''t solve the problem, now you have a spare. Not a bad thing.


sanuni 01-30-2002 11:55 AM

Cooling pump blues
Good point.
SOLUTION FOUND! It was a bad gasket. I just installed a new gasket and now it pumps like a champ!

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