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  1. #1

    Pump bearing and setup questions

    I have a 2005 rxp with the Skat double bearing mod. I only put around 35 hours a year on the ski and have the bearings replaced each year. Every year I find a lot of metal shavings in the pump cone mixed in with the gear oil. The bearings spin rough as well. I just pulled my pump and this time found the entire cone filled with black lube and water. It was filled to the point that when I removed the cone the cone pushed out towards me under pressure. Obviously, something has failed in a seal. Never had the cone full before. Questions:


    • Anyone else have issues with the Skat double bearing mod causing metal shavings?
    • Do people just use the stock pump bearings on higher hp skis or do they have Skat do the bearing mod still?
    • $3000 for either the Rotax pump or the Skat racing pump is a little steep. Any other options out there to get a little more out of the stock pump?
    • What is the ideal pump setup for racing applications?
    • I had a GP1200 back in the day that Skat would modify by cutting out the stock vanes and inserting a new 12 vane assy. Anyone do that mod currently?
    Being that pumps are only around 50% efficient, I would think there would be room for performance gains in this area.

    Mark


  2. #2
    Vern's Avatar
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    Hi Mark, I have two Skat mod pumps, each with about 100 hours on them. I have never found shavings in them when I changed the oil, and I usually put 30 - 50 hours on the oil before changing it. They both rotate very smoothly and I have not had water intrusion yet. Sounds like your front seal has failed I would guess.

    It sounds like the more power you make, the bigger diameter pump you can run efficiently. Not sure of the optimal size for a stage 3+ RXP, but our stock size pumps seem close ... Since they are only 50% efficient I have always wondered about ways to make them more efficient too ... number of vanes, length of vanes, etc.

  3. #3
    idoodou's Avatar
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    are you useing pump oil or pump grease i have seen the pump grease turn black when water mixes with it and yes there should be a more efficient pump 50% just sucks

  4. #4
    Moderator Snoman's Avatar
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    Mark you know my setup and i have been running the OEM pump for the last 4 years now with no issues.I too run oil in my pumps and have not seen any blacking to either of them..NOW im not running an ECU like you but as you know our boats are very close to each other...I would think something is amiss alignment wise with the shaft and bearings seeing your getting shavings and it spins hard..When i had the tripple bearing pump it still spun fairly easy....IMO go back to the stock pump/bearing combo..there really isnt much failure with these and As you know Tommy and a couple other big guns here run the OEMs too with no issues..

  5. #5
    Quote Originally Posted by Snoman View Post
    Mark you know my setup and i have been running the OEM pump for the last 4 years now with no issues.I too run oil in my pumps and have not seen any blacking to either of them..NOW im not running an ECU like you but as you know our boats are very close to each other...I would think something is amiss alignment wise with the shaft and bearings seeing your getting shavings and it spins hard..When i had the tripple bearing pump it still spun fairly easy....IMO go back to the stock pump/bearing combo..there really isnt much failure with these and As you know Tommy and a couple other big guns here run the OEMs too with no issues..
    After the rebuilds the pump spins freely. Never had a problem with water in the bearings until this year. Did notice that the bearing side of the pump shaft is .010 larger diameter than forward of the step in the shaft where the seal sits, so the inner seal isn't doing much good. May be time for a new shaft. Also, I have been torquing the impeller to the 54 ish ft/lbs that the manual called for. I read your post where that spec is wrong. Seeing how the pump bearings and shaft are designed that may have caused some issues. The 3 blade may cause a little more shaft flex than the 4 blade as well. If I was rich, I would just get the Rotax pump.

    Mark

  6. #6
    Moderator Snoman's Avatar
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    Mark,
    On my triple i could take the pump, turn it upside down, and literaly tap it on the bench and the bearings would fall out...54 Ft/LBS is way to low as you now know..i always torque my props to 90/92 ft/lbs..Could the bore in the pump be getting wore out from being rebuilt every year???Letting the bearings shift or bind up a tad therefor causing your wear??Just a thought..

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