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Thread: Rebuilding water pump interval on a Yamaha F90 4 stroke

  1. #1
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    Default Rebuilding water pump interval on a Yamaha F90 4 stroke



    Hello folks,

    I have a new 2012 90 hp yamaha on an 18 foot aluminum boat. I run it on the silty Yukon River, normally around 4800 to 5000 rpm. Any ideas on how often I should change or rebuild the water pump. I assume it would be more often because of the silty river. What are other folks experience with muddy waters?

    Norm

  2. #2
    Member Akgramps's Avatar
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    I would inspect it every year unless you put a lot of hours on, on my jet running a variety of rivers (interior), the pump usually is starting to look a little sad after 150 hours....but thats my outfit.

    The pump seems to last longer with the prop on, but I am usually in the ocean with the prop. Silt can be rather abrasive.

    On some you can just replace the cup, impeller and the plate, pretty inexpensive actually. On mine they do not offer just the cup....so have to buy a complete new pump.
    “Nothing worth doing is easy”
    TR

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    Member akjeff's Avatar
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    In silty water the liner is what wears down first. I would run it until failure. And carry a spare water pump and liner with me. Maybe even a housing. If you are checking it, you might as well just change it. If changing any of it, change all of it. So, that being said it is more economical to just run it until it fails and be prepared with a complete new assembly. Just my two cents.

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    We recommend every 2 years or 200 hours for the impeller. The rubber vanes can wear down in the silty water, so you may want to change your impeller more often if you are finding excess wear. You will also find wear on the base plate and cup and need to replace those periodically. You can buy a water pump kit which has all the parts so you'll have them when you need them and just replace what you need to. You can also buy just the impeller or base plate as needed. It isn't a tough job to drop your lower unit and take a look, so better to look at it yearly weather you replace anything or not since you are running in a more abrasive condition. Age can also affect your impeller, the rubber loses its "spring" and wont' make as much water pressure. If you take your cup and housing off and the vanes don't bounce back after a bit, they are getting old and need to be replaced. The problem with going until a water pump fails, especially with a prop, is that you will 1. overheat your motor which can damage your thermostat and cause oil dilution, and 2. your impeller can disintegrate and clog up your water intake and cooling system with little bits of rubber. Not to mention having to work on your motor on a sand bar rather than your garage. In a half hour's time you can get in and out of your water pump and know that it is good to go, seems easy enough to do once a year.
    Casey
    Yamaha Dealer
    Petersburg, AK

  5. #5
    Member MARV1's Avatar
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    I live at the mouth of the Yukon, yes, silty water and the F90 impellers are too small and thin for the size of outboard it is. Wish they made these with the F115 lower unit and impeller, would make for a much more durable and reliable outboard and setup! Blew/cracked 2 impellers, one after 10 hours of use and 2nd about 300 hours and it makes sense to just carry a spare and tools when it goes...
    The emphasis is on accuracy, not power!

  6. #6
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    Thanks for the great replies. I will be monitoring the pump every 100 to 150 hours for sure.

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