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2012 T9.9LPHA Water Pump Replacement after Overheat

NorCal

NorCal

Member
Had my low-hours 2012 T9.9LPHA overheat and stop while trolling. Hoping that I didn't do serious damage but haven't had a chance to check to see if it will turn over to do a compression test. Am assuming that the cause was a bad Water Pump Impeller as it was overdue to be replaced. Any knowledgeable advice on how to proceed in checking things out and replacing the water pump, if the powerhead isn't fried, would be greatly appreciated as I can't afford to have a shop do it.
 
Hey mate, don’t panic yet — these are tough motors.
First, don’t try start it. Pull the plugs and turn the flywheel by hand. If it spins freely, that’s a good sign.

Most likely it’s the water pump impeller, especially if it was overdue. Drop the lower unit and replace the impeller (ideally full kit). Check the housing and make sure the key is in place.
Before reassembling, check the water tube grommet and make sure nothing’s blocked.
Once back together, run it on muffs and check for a strong telltale. If it’s weak, shut it off straight away.
After that, do a compression test — cylinders should be within ~10%.
If it shut down quickly, chances are it’s fine 👍
 
JY Marine said:
Hey mate, don’t panic yet — these are tough motors.
First, don’t try start it. Pull the plugs and turn the flywheel by hand. If it spins freely, that’s a good sign.

Most likely it’s the water pump impeller, especially if it was overdue. Drop the lower unit and replace the impeller (ideally full kit). Check the housing and make sure the key is in place.
Before reassembling, check the water tube grommet and make sure nothing’s blocked.
Once back together, run it on muffs and check for a strong telltale. If it’s weak, shut it off straight away.
After that, do a compression test — cylinders should be within ~10%.
If it shut down quickly, chances are it’s fine 👍
Click to expand...
So, the good news is the motor turns over and isn't seized. The not so good is that the Impeller was disintegrated and most of the vane pieces are nowhere to be seen. Is there a way to flush out any pieces that may be in the Powerhead Cooling Passages? Also, should I replace the Housing or does it look okay to put a new Pump Cup in & reuse the Housing?



 
Good news it’s not seized 👍
Since the impeller broke up, you need to flush out the missing pieces—they can block cooling passages. Remove the thermostat and flush from the powerhead side by putting a hose into the thermostat housing and running water down through the block, so it pushes debris back out the water tube. You can also disconnect the water tube and flush top-down that way. Check the thermostat housing too, bits often get stuck there.
As for the pump, if the housing has any scoring or heat marks replace it. Honestly I’d just do a full water pump kit for peace of mind.
Make sure you’ve got a strong telltale before running it again.
 
JY Marine said:
Good news it’s not seized 👍
Since the impeller broke up, you need to flush out the missing pieces—they can block cooling passages. Remove the thermostat and flush from the powerhead side by putting a hose into the thermostat housing and running water down through the block, so it pushes debris back out the water tube. You can also disconnect the water tube and flush top-down that way. Check the thermostat housing too, bits often get stuck there.
As for the pump, if the housing has any scoring or heat marks replace it. Honestly I’d just do a full water pump kit for peace of mind.
Make sure you’ve got a strong telltale before running it again.
Click to expand...
Thanks for your help/advice! Another question -are Sierra parts of good quality these days or should I stick with OEM Yamaha?
 
Sierra parts are generally decent, but for something critical like the water pump/impeller I’d stick with OEM Yamaha. Not really worth the risk with cooling components—OEM is more reliable.
 
JY Marine said:
Sierra parts are generally decent, but for something critical like the water pump/impeller I’d stick with OEM Yamaha. Not really worth the risk with cooling components—OEM is more reliable.
Click to expand...
Ordered all OEM Yamaha parts - Water Pump Service Kit, sans Pump Housing, as mine looks to be in good shape, and also a new Thermostat, Seal, & Gasket. Found the other four large impeller vane pieces that were missing down behind the intake pickup screens. Will check in the Thermostat housing area for any small pieces and will flush as you suggested.
 
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