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75 Force/Merc not pumping water

1

1ton

Contributing Member
I put a water pump kit in per service manual instructions and this thing will still not pump water! Has anyone ever encountered this problem? Only thing coming out of the pee tube is exhaust gas. They're no obstructions in the lower unit. I have never encountered this type of problem and could use some advice. Thank you for your time :)
 
I have the gear case submerged in a tank. I know some Force engines wont pump off purge cups. The drive key is in place because I put the impeller on and turned the drive shaft clockwise while pushing down on the housing to install the pump. The connection tube is correctly in place as well.
 
1) Can you pull the connection tube off where it connects to the block and see if water comes out of the nipple? If so, your hose is blocked.
2) How much time are you waiting when running the motor to see water come out of the tell tale? If only 10 seconds, is it possible your thermostat is stuck open and allowing water to immediately travel through the block for cooling, which takes time for it to circulate before being discharged out the tell tale?
3) Does your overheat alarm sound at all?
 
That was it! Thank you so much. Is it just the Force engines that are not self priming? How do I identify pumps that are not self priming to avoid this in the future? Again, thank you for your help :)
 
1ton said:
That was it! Thank you so much. Is it just the Force engines that are not self priming? How do I identify pumps that are not self priming to avoid this in the future? Again, thank you for your help :)
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For any outboard with a pump in the lower unit, run in a test barrel, standard practice is to have the pump fully flooded. Generally you'd want the water level in the test tank to be at least halfway up the mid-section (exhaust tower). This ensures the pump is completely flooded and should pump properly.

Note that some engines are sensitive to test barrel size and aeration in the barrel. I've had a number of older Big Twin Johnrudes that absolutely wouldn't pump in the barrel. A real pain. Most of the Mercs are OK in the "bucket", but with the larger engines, you've got to be careful to keep the water level up when you're running the engine. A large enough "bucket" will allow you to idle in gear but watch the water fly out if you rev it up! :eek:

Cheers...........ed
 
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