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Thread: lower jet unit

  1. #1

    Question lower jet unit

    I have a yamaha 40 jet that I bought from my dad, he had the lower jet rebuilt about 3 years ago. He barely used the motor the first year after he had it rebuilt. I bought the motor and used it all last summer and greased it after every use, I have been useing it this summer about 5 times and greaseing after every run. The question is how long does the lower jet units last.
    Thanks for your help
    Big Daddy

  2. #2
    Moderator Paul H's Avatar
    Join Date
    Apr 2006


    It depends on how much gravel you suck throuh it. If you keep out of the gravel it'll last a long time, make a habit of shooting gravel through it and you could probably trash one in a season.

    Most of the outboards will last for decades of recreational use if properly maintained and not abused.

  3. #3
    Member akjeff's Avatar
    Join Date
    May 2007

    Default Grease

    The grease protects the bearing inside the unit. When you pump in the grease out comes the water (from the bearing). Protection from corrosion. If the main part of the jet unit is intact and not cracked everthing else is replacable. If the shaft is straight, bearing is good, the intake foot and grate are intact and the main impellor is in good shape everthing else is routine maintenance and wear items. The water pump can take a beating from sand, silt and gravel. I ran my jet pretty hard last fall ,ran a lot of sand, silt and a little gravel through it. This spring I replaced my water pump impellor, housing and bottom plate and the main impellor liner or wear ring. And I am almost back to 100 %. My intake foot and grate took a little bit of beating also, I am considering replacement.


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