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Impellers impellers

  1. #1
    d4l is offline
    Junior Member d4l's Avatar
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    Apr 2016

    Default Impellers impellers

    How often do you all replace your impeller? Some say every year, some say every 300 hours, every 3 years, every 5 years, when needed! For someone who don't have all the special tools it's a bitch to get down there. It has ran about 10 hours, was replaced 2 summers ago. It's a mercruiser alpha one gen II. Thanks

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  3. #2
    Senior Member SANGER SS396's Avatar
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    Dec 2007
    North Las Vegas

    Default impeller

    i retired from working as a marine mechanic.
    we would tell our customers that it should be replaced every 2 yrs
    also you need to regrease the input shaft every 2 yrs and at the same time do an inspection of the
    as a side note the only time the drive should be in the up postion is when you are driving down the road.
    this will save your bellows and they will last much longer.
    if you want you can pm me with your phone number and best time to call you i would be happy
    to chat with you on this subject

  4. #3
    kenny nunez
    Join Date
    Oct 2014
    Kenner, La.

    Default impeller

    x2 on the the drive service, I was a Mercruiser dealer also. The only thing I would add is to be sure the pocket where the shift slider moves is cleaned out and the alinement checked.

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  6. #4
    Senior Member
    Join Date
    Dec 2007
    New Jersey


    I worked for a MerCruiser dealer for about 5 years and have owned and operated boats for more than 45. Replacing the water pump impeller every 2 years is good practice for a number of reasons.

    1. If you boat in salt water corrosion continues to work year round. If you wait until the impeller fails, corrosion may make it impossible to get the drive apart for service.

    2. The impeller is only a synthetic rubber, with vanes that flex to pump the water. If you have run aground or in silty water, it is likely that you have run sand through the pump and damaged the impellor.

    3. While the engine is stored, the impeller sits with half of the vanes bent and half straight. Many times as an impeller ages, the vanes will take a 'set' and stay bent so the pump will not work to capacity. This would show up as the engine runs cool at mid throttle, but overheats at near Wide open throttle. One season I decided to wait "one more year", got out on the water and overheated at anything more than mid throttle. When I took the impeller out, half the vanes were still bent.

    4. If the impeller fails while you are boating, it will at the very least ruin your day on the water but could very well overheat and damage your engine.

    5. If the impeller fails and breaks into pieces it is a pain trying to get all the pieced out of the cooling system and the pieces not found will block flow and cause overheating.


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