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Water Pump Issue/Impeller Melting

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Willkve

New member
Hey y'all. About a year ago I bought a boat off my buddy and its got a mercury outboard 40hp 2 stroke motor serial no. 6416658. It's got some issues that we're fixing right now.

We connected the motor to muffs and water was not jetting out the train tube. We thought it might be clogged so we took the lower part of the motor off and opened up the impeller housing. Upon doing so, we discovered the impeller was completely shredded. I ordered a new one and today we installed it. We connected everything back up and tried to flush it again. We noticed it was suck in gear so we took it all apart again and the new impeller was completely melted and part of the housing. When we tried to flush water through it, we did notice the arm that connects to the gear shaft (not sure what it's called) on the top part of the motor under the carb wasn't aligned properly. This is my guess for the new impeller getting melted. I ordered a new water pump kit that'll arrive next week, so hopefully that'll solve our issue. Have any of y'all had this issue before, or know why this might be happening?
 
racerone said:
Impellers melt when there is no cooling water.----There is no other reason why they melt.
Click to expand...
Got it. It seemed like there was water getting to the impeller but I guess not enough. How do you think the water isn't getting to the impeller? a clog somewhere?
 
This is how I install the LU in about 60 sec.: Turn the LU shift shaft by hand counter-clockwise until it
stops, then with Vise Grips tight on the bottom of the shaft turn it a
few more degrees CCW until it clicks into a stop, this
should be neutral - check by turning propshaft --
prop should spin freely.
Put control in N and go ahead and attach LU to driveshaft housing some turning of the flywheel will help the DS splines align.
Do not shift into reverse unless you turn the prop at the same time.




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When the new pump is installed try a barrel instead of muffs, some outboards just don’t like muffs. You will have to make sure the water in the barrel is 3-4” above the water pump. Before setting the impeller into the housing apply a thin film of waterproof grease on the housing or impeller, this will help with initial startup. Pull the intake screens off the LU and check for blockage.
 
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