Yamaha F150TXR

[Bduck]

Ever since I did the vinegar flush last October I would get the alarm at high rpms when doing a maintenance run on Willard. NMEA showed that my motor temp was slowly rising but if I kept it under 5000rpm the alarm would not sound off. Temp would be higher than normal and when throttling back to much lower rpm temp would come down within reasonable operating temp. My thoughts were an obstruction within cooling passage in the motor after vinegar flush loosened up crud. I replaced poppet valve with a new kit which consisted of a grommet, valve, tension spring, and outer housing gasket. The old valve appeared to be in good shape but the grommet appeared to be worn flat on one side of where valve seated against it and had some crud buildup but not enough for any blockage. From previous pic posted I didn't remove grommet just in case it was at brittle stages.

Old Valve                    Old & New Valve
 

After replacing poppet valve I did another maintenance run but my confidence wasn't there that this would help solve over temp issue and it didn't. I'm glad Willard is a short distance for me to run my boat. Next step is I removed lower end of gear housing and this is where I found the issue of over temp.
 
                                     Plastic Impeller
[i]Worn Impeller                     Housing                    Side View[/i]
  

After removal of impeller housing found impeller going thru a deterioration of a melt down. Impeller housing is plastic with a metal insert. To the right side of housing is a passage where lake water is sent up to the motor. This passage is partially closed off with melted plastic. After talking with 2knots (Alan) he had same thing to happen with his motor and we both have same exact year motor. He came to the conclusion that this was the result of running motor on earmuffs not having enough water pressure to circulate. I came to agree with this as I had to shut down my motor a few times when I couldn't get enough pressure to get water to come out at pee hole. I did notice that my house pressure is much lower than my irrigation pressure and that's what I mostly used to make it work. Made purchase of impeller kit with housing, all in stock with 2 day immediate shipping.

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