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  1. #1
    Lieutenant Junior Grade
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    Default Water circulating pump - how do you know when it is bad?

    1991 4.3LX

    I'm continuing to learn about the open cooling system on these sterndrive systems.

    I haven't seen anything in the manual or on the site to explain how to understand if one's water circulating pump is working properly. I know on my older cars, if the water pump wasn't leaking, it was probably ok. Is it the same for these?

    I'm in the process of troubleshooting an overheat problem. Water isn't flowing properly and I'm getting it isolated, but as I go through this thing, I want it to be 100% when I'm done.

  2. #2
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Water circulating pump - how do you know when it is bad?

    I know on my older cars, if the water pump wasn't leaking, it was probably ok. Is it the same for these?
    Same thing.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
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  3. #3
    Petty Officer 2nd Class
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    Default Re: Water circulating pump - how do you know when it is bad?

    Overheating can be a lot of things. For the raw water cooling, look for a hose coming off of your transom that feeds directly into the engine water pump. Take that off, crank up your engine with bellows on and see if you got a good water flow coming into the engine water pump. Check to see if you got water in your engine oil, a tell-tale sign of other problems that could lead to overheating such as warped heads, cracked block, blown head gasket. Could also be stuck thermostat. You got to narrow it down.
    '96 Marada MX1, 3.0LX, A1GII.

  4. #4
    Lieutenant Junior Grade
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    Default Re: Water circulating pump - how do you know when it is bad?

    Thanks Schmoe. I have been working my way through the diagnostic process.

  5. #5
    Petty Officer 1st Class
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    Default Re: Water circulating pump - how do you know when it is bad?

    If it leaks, the pulley wobbles, or it starts making funky noises, then its probably bad. I've never seen a circ pump fail in such a way that it stopped moving water though. Its a stainless impeller that makes no contact with anything, so basically all thats to wear out are the seals and the bearings in the shaft. Usually its a seal that goes first, and the water washes out the bearing, making it fail.
    1993 Rinker FiestaVee 300
    twin 5.7L/Bravo
    newly appointed with Bravo III lower units

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