Hello and thanks for any help in advance from the members of this awesome website.
After reading every thread I can find on the subject of impellers and raw water pump issues, I am still very mystified by a lack of water pressure from my raw water pump. I will try to be brief but….
I have an ongoing overheat alarm, after the engine warms up with boat in water. Despite impeller change, hose clamp tightening, new o ring where pump housing bolts to motor, and one particular “AHA” moment, finding a piece of a previous owner’s impeller vane in the thermo housing, I am no further ahead.
Dealer says pump and impeller look okay and should pump, with normal wear showing, and a slight groove starting to show in the outside edges of the impeller vanes where they pass over the ridges between the inlet and outlet ports inside the pump. (Excuse my best guess at the names of parts etc). He tightened a clamp I had missed on the tube coming in through the transom, and ran the boat at normal operating temp for 20 min on a hose/muffs.
I did the same and could feel cold water entering the exhaust manifolds which had been getting very hot after less than 1 minute in the river at cruising speed, just before the alarm came on.
I am an hour drive away from a store with large clear hoses, gauges, barbs etc, as indicated in the VP diagnostic posted in Don S’s sticky. So I simply removed the upper end of the hose from the pump to the thermostat housing and sucked on it. I was able to suck water from the outdrive into and through the pump, and of course blow air back through. I filled that hose with water and covered the top inlet pipe on the pump with my hand and blew like a madman. No water leak anywhere. Drained all water and blew air into pump. No air leaks. Connected a 2 foot hose to the top inlet of pump and filled hose with water with a bow in it below the pump down into the bilge and back up. Start engine, no suction whatsoever. Switched hose to bottom of pump ‘cause I’m so rattled and confused now I am second guessing everything. Same thing, water lays in hose until I lift it and pours out other side of pump.
Splined shaft from motor is in good shape and turns with motor. Vanes are tilted in correct direction for rotation.
Just about to jump off the roof, as whole family watched this debacle all weekend, involving my very handy buddy and I. Total humiliation. No fishing or tubing for the second straight beautiful weekend.
I read that diagnostic again and noticed the part about the impeller hub spinning free, or something along those lines. Could it be that a new impeller which worked for several hours a few weeks ago has come apart inside? I did not specifically test that by holding it and trying to twist the center with a big screw driver or something.
I guess I’ll haul the darned thing off again and check? If it is okay, do I need to drive to the city and buy a bunch of plastic hoses and gauges etc? Can anyone think of some other obvious or not so obvious cause of no pump pressure at all?
I can only assume that the garden hose pressure is pushing enough water through the pump etc to cool the manifolds while in the yard?
Thanks for reading this sad essay. TB
After reading every thread I can find on the subject of impellers and raw water pump issues, I am still very mystified by a lack of water pressure from my raw water pump. I will try to be brief but….
I have an ongoing overheat alarm, after the engine warms up with boat in water. Despite impeller change, hose clamp tightening, new o ring where pump housing bolts to motor, and one particular “AHA” moment, finding a piece of a previous owner’s impeller vane in the thermo housing, I am no further ahead.
Dealer says pump and impeller look okay and should pump, with normal wear showing, and a slight groove starting to show in the outside edges of the impeller vanes where they pass over the ridges between the inlet and outlet ports inside the pump. (Excuse my best guess at the names of parts etc). He tightened a clamp I had missed on the tube coming in through the transom, and ran the boat at normal operating temp for 20 min on a hose/muffs.
I did the same and could feel cold water entering the exhaust manifolds which had been getting very hot after less than 1 minute in the river at cruising speed, just before the alarm came on.
I am an hour drive away from a store with large clear hoses, gauges, barbs etc, as indicated in the VP diagnostic posted in Don S’s sticky. So I simply removed the upper end of the hose from the pump to the thermostat housing and sucked on it. I was able to suck water from the outdrive into and through the pump, and of course blow air back through. I filled that hose with water and covered the top inlet pipe on the pump with my hand and blew like a madman. No water leak anywhere. Drained all water and blew air into pump. No air leaks. Connected a 2 foot hose to the top inlet of pump and filled hose with water with a bow in it below the pump down into the bilge and back up. Start engine, no suction whatsoever. Switched hose to bottom of pump ‘cause I’m so rattled and confused now I am second guessing everything. Same thing, water lays in hose until I lift it and pours out other side of pump.
Splined shaft from motor is in good shape and turns with motor. Vanes are tilted in correct direction for rotation.
Just about to jump off the roof, as whole family watched this debacle all weekend, involving my very handy buddy and I. Total humiliation. No fishing or tubing for the second straight beautiful weekend.
I read that diagnostic again and noticed the part about the impeller hub spinning free, or something along those lines. Could it be that a new impeller which worked for several hours a few weeks ago has come apart inside? I did not specifically test that by holding it and trying to twist the center with a big screw driver or something.
I guess I’ll haul the darned thing off again and check? If it is okay, do I need to drive to the city and buy a bunch of plastic hoses and gauges etc? Can anyone think of some other obvious or not so obvious cause of no pump pressure at all?
I can only assume that the garden hose pressure is pushing enough water through the pump etc to cool the manifolds while in the yard?
Thanks for reading this sad essay. TB