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12 vane vs 8 vane impellers

Discussion in 'Engines' started by Capt Ralph, Jun 4, 2024.

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  1. Capt Ralph, Jun 4, 2024
    #1
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    13,270
    Location:
    Satsuma, FL
    Changing out impellers today. Renewed a question from the back of my mind;
    What moves more water, 12 or 8 vane impellers?

    Lots more rubber, smaller chambers in the 12 vane impeller.
    Lil less rubber, larger chambers between the vanes on the 8 vane impeller.

    I have a call into Depco Pump but those guys do this lunch thing. I may be called back after their siesta.

    What does the Yachti Forums think?

    20240604_120126a.jpg
  2. SplashFl, Jun 4, 2024
    #2
    SplashFl

    SplashFl Active Member

    Joined:
    Feb 2, 2021
    Messages:
    492
    Location:
    S. Florida _ Bertram 46
    Never had an 8 but the 12's always lasted a LOT longer then the 6.
  3. Capt Ralph, Jun 4, 2024
    #3
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    13,270
    Location:
    Satsuma, FL
    My new sales contact (previous contacts passed and the next just retired) did reply this afternoon.
    Joe tells me that the 12 vane pumps the same as the smaller vane count but runs cooler and last longer.
    I still don't see the big picture of this but he is supposed to be the expert.

    We did agree that long ago, the cam height was the factor in water movent. These variables have long been removed from this (and many) pump(s).
    These changes also happened during the life of my 46 year old Detroits.
    Per my original part manual, so many part numbers have been superseded to just a few. I fear the 6980 pump in my application has been down graded for simple logistics.
    Lately rated as a N pump. Not a TI pump as 46 years ago, as we have now.

    Just sent Joe a email asking about the Jabcso 18780 & 18760 pumps. Less vanes, more water for slightly taller HP engines.

    Now that our bad stb shaft has been finally replaced. No more teeth grinding at intermittent speed atemps. I want our sled to run with the whales,,, with out getting real hot after a few minutes..

    Before the galleries start typing,,,, The HE and dump cans are clear. Fresh props, bottom, thermostats, mechanical temp gauges. I have practiced what I preached...
    And yes, fuel pressure up, boost is good. Air box pressure is good. No dark smoke.
    Also; We have moved off the boat, no clothes, extra tools, spares and family junk. Boot stripe is way above the water.

    But now, it is our boat and I don't like temps crawling up past 190° while making 600+ HP for more than a minute or longer.

    Also, Once this issue is under control, up dating injectors to 7N95s or larger. I will need to ensure all cooling in good before this.

    Anybody taken these dives before??