Cooling Problem 79 Johnson 6 hp

MBurandt

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May 3, 2014
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7
Having replaced the water pump there is no water coming up to the top of the head at the thermostat when the motor is running, but when I take off the flywheel, remove spark plugs and attach a drill to turn the motor water does flow up. Is there a back pressure of some kind that prevents upward water flow when the motor is running? Thanks.
 

oldcatamount

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Apr 4, 2010
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Re: Cooling Problem 79 Johnson 6 hp

Probably an RPM thing. Your drill technique will spin the motor many times faster than when the motor is running at idle. Was the old impeller shredded or just worn out?
 

MBurandt

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Re: Cooling Problem 79 Johnson 6 hp

The impeller was worn out. The drill is variable speed and the water pumps up into the head at slow or fast speeds, but as soon as I run the motor water stops. Could there be a back pressure stopping the flow?
 

racerone

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Re: Cooling Problem 79 Johnson 6 hp

Is the water in your " test tank " well above the pump ?
 

racerone

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Re: Cooling Problem 79 Johnson 6 hp

Back pressure has nothing to do with the water going through the block.-------Are the new water pump parts factory original or aftermarket ?-Any pictures of original parts that you replaced and the replacement parts ?
 

MBurandt

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Re: Cooling Problem 79 Johnson 6 hp

Back pressure has nothing to do with the water going through the block.-------Are the new water pump parts factory original or aftermarket ?-Any pictures of original parts that you replaced and the replacement parts ?

The pump replacement parts are from the dealer so they would be correct. I attached a drill to the shaft before attaching the lower leg and the pump worked fine. It also worked when I attached the leg to the head and again used the drill, but when actually running the motor water stops, so there must be an interference with the exhaust. I don't have pictures.
 

boobie

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Re: Cooling Problem 79 Johnson 6 hp

Do you notice any smoke coming out around the power head base gasket ?
 

MBurandt

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Re: Cooling Problem 79 Johnson 6 hp

Do you notice any smoke coming out around the power head base gasket ?

No smoke from the power head base as I used a new gasket. There is water coming out the smaller drain hole half way down and also exhaust gas coming out the pee hole, but no water at the top of the head where the thermostat is located. Seems like some water is circulating in the lower part of the head.
 

racerone

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Re: Cooling Problem 79 Johnson 6 hp

Are you 100 % sure the water tube is in the discharge of the pump ?
 

boobie

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Re: Cooling Problem 79 Johnson 6 hp

If you replaced the P/H gasket did you get the right one ??
 
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