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Raw water pump leaking to bearings

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  • Raw water pump leaking to bearings

    Hi All, I have a 93 baja with a 454 mag ho GenV second or third impeller change I noticed water in the mech. fuel pump reservoir and the bearings were going bad due to water in them rust etc. removed pump and replaced bearings with sealed units and removed mech. fuel pump and blocked off with plate and added a Mallory 4-8 psi electric fuel pump. 2-3 years later I am replacing the impeller again and find traces of water in oil reservoir which was dry since the removal of mech. fuel pump. I also noticed when engine/water pump is not running and hose is still connected to water inlet hose a fairly nice 1/8 inch stream of water shooting out the weep hole in the side of the pump just in front of the mount area.
    I use a custom made fitting that connects to the garden hose and then connects directly to the inlet hose that I remove from lower unit at transom wall after an episode with the muffs falling off while running it by myself and lunching the impeller. I realize that is pressurizing the inlet and the impeller area of the pump but should water be passing thru the bearing area into the reservoir where oil would normally be? I would think not but this is obviously happening during normal running conditions or there wouldn't be rusty water in the reservoir area. What path does bypass water take to get to the weep hole if it's not going thru the bearing area? Thanks for the insight

  • #2
    Re: Raw water pump leaking to bearings

    Well it seem you have exceeded the 12psi pressure that the bearing seal is rated t by having the water hose attached to the inlet side of the pump while the pump is not running and sucking the water thru. The bearing seal rated at 12psi then passes the water to the bypass or pressure relief hole that coincidently is right adjacent to the actual bearing and water then gets into the bearing and eventually into the mechanical fuel pump actuating chamber where the oil is and contaminates the oil if its in there and destroys the bearings.

    So R & R the bearings and seals reassemble and install new impeller being careful to note correct rotation the impeller blades if installed in the wrong direction will not fold over the correct direction when the pump starts rotating they will just shear of and you will have to replace again.


    • #3
      Re: Raw water pump leaking to bearings

      Thanks for that response it was very helpful.


      • #4
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        Re: Raw water pump leaking to bearings

        No problem just thought it might be good info for others to read that had a similar issue.