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  1. #1
    Join Date
    Apr 2016
    Location
    Houston
    Boat
    Sea Ray
    Details
    2004 280 Sundancer
    Engine(s)
    Twin 4.3 MPI
    Posts
    5

    Stern driven water pump conversion to engine driven water pump

    I own a 2004 Searay 280 Dancer. In a couple months I will be putting her on the dry dock for maintenance. During this time, I will be removing both Mercruiser outdrives and have them repainted, replace both u-joints, oil seals and check for bent shafts. I was also thinking about adding an engine driven water pump. Presently the cooling water comes from the outdrives. Can the impellers be removed in the outdrives? and install allow the new engine driven water pump to pull water from the outdrive. The boat does not have an extra seacock.



    Has anyone had any luck with this?

    2004 280 Sundancer

  2. #2
    Join Date
    Dec 2007
    Location
    East Coast Florida
    Boat
    Sea Ray
    Details
    300 Sundancer
    Engine(s)
    5.0MPI Bravo III
    Posts
    1,446

    Re: Stern driven water pump conversion to engine driven water pump

    you could do it with Mercruiser parts.....but I would use crank mounted pumps - you get a better designed pump and easier access for impeller changes......I would also add seacocks - never have to worry about drive cooling restrictions and get a way to shut off the water coming into your boat....just be sure to cut the feed hose on the drive so it still gets the flow through cooling......if this sounds like too much work, its not a problem drawing from the outdrive....

  3. #3
    Join Date
    Jan 2008
    Location
    Elk Grove, California
    Boat
    Cobalt
    Details
    23' CM23
    Engine(s)
    GM SB 383" Stroiker" Alpha Gen I
    Posts
    2,111

    Re: Stern driven water pump conversion to engine driven water pump

    Mercruiser actually has the parts available to do this. My 1985 Cobalt has the engine mounted in the middle of the boat, not the stern, and has a drive shaft back to the Alpha drive. Merc called this a Jackshaft model. I have an engine-driven water pump through the bottom of the hull like an inboard. All of the plugs and special parts to block off the stern drive pump water supply are there. However, I was always told to keep the pump in the stern drive as it pushes cooling water to the upper gear case so I've always maintained that pump. Seems like a drive shower would do the same thing. I do not have the hose that goes through the upper unit through to gimbal housing and to the motor. There is a special block-off part that replaces the copper tube that goes through the gimbal housing.

    Go to one of the Mercruiser parts suppliers on line and do a search for "Jackshaft Model"

    NorCal Boater
    Previous Boats
    1989 340 DA, 1987 S-24 Sorrento, 1985 Cobalt CM23 (Mine again)

  4. #4
    Join Date
    Jun 2015
    Location
    West Michigan
    Boat
    Sea Ray
    Details
    1999 Sundancer 340
    Engine(s)
    454 Mercruiser's w/ V Drives, Westerbeke gen set
    Posts
    404

    Re: Stern driven water pump conversion to engine driven water pump

    Would this change cause you to be less likely to maintain your outdrives overall? If so...don't do it!

    I've been deeply scarred by an Alpha drive in a past life. It was a horribly abusive relationship.

  5. #5
    Join Date
    Jun 2009
    Location
    Lake Norman, NC
    Boat
    SeaRay
    Details
    1999 185 Bowrider,
    Engine(s)
    Mercruiser 4.3, Alpha I
    Posts
    1,002

    Re: Stern driven water pump conversion to engine driven water pump

    I would question the economics of doing this - unless you have something else going on, those pumps are in the $300-$400 range plus any other stuff to covert it - belts hoses etc.. The Merc engine mounted pumps are not really known to have the service interval of an Alpha I Gen II pump (the old Alpha I pump is a different story). The engine mounted pumps use a small impeller and run at the engine RPM, the Alpha I Gen II pump runs at the drive speed which is slower than the engine - depending on the drive ratio. The Alpha I impeller is much larger than the Bravo / Engine pump and they tend to last longer. I usually get 3yrs out of mine and they still look good - never had one fail. I have heard of people going much longer. Having the pump in the outdrive is a bad design from a service standpoint, but otherwise the Alpha I Gen II pump, and drive for that matter is solid. Even the engine mounted pumps can be a real chore depending on the boat and installation. I personally would not do it.
    ______________________________
    1999 SeaRay 185 Bowrider - Current
    2000 SeaRay 290 SunDancer - Previous
    1979 Correct Craft Ski-Tique - Previous
    1948 Chris Craft Custom Runabout - Oh man to have that one back!


  6. #6
    Join Date
    Dec 2007
    Location
    Homeport: Charles City, VA
    Boat
    Sea Ray
    Details
    1999/2007 330 Sundancer Hardtop.
    Engine(s)
    6.2 Merc Horixons 1.5:1 Velvet Drives
    Posts
    4,174

    Re: Stern driven water pump conversion to engine driven water pump

    Agree with NorCal. Thru hull, strainer, crank pump and drive shower. Technically, I don't know about the water cooling the gears from the inside. However, a friend had a pair of mercs on the back of his go fast and prior to drive showers, you could have fried an egg on the upper unit after even a mild run of say 40 knots.
    Best Regards,
    David

    "Saint Max", '99 330 Dancer
    2007 6.2L Mercruiser Horizons; 1.5:1 Velvet V5000 "V" Drives

  7. #7
    Join Date
    Apr 2016
    Location
    Houston
    Boat
    Sea Ray
    Details
    2004 280 Sundancer
    Engine(s)
    Twin 4.3 MPI
    Posts
    5

    Re: Stern driven water pump conversion to engine driven water pump

    Thanks for all the input guys. The upgrade was for the ease of maintenance on the impeller.
    2004 280 Sundancer

  8. #8
    Join Date
    Oct 2015
    Location
    Long Island
    Boat
    SeaRay
    Details
    2004 340 SeaRay Sundancer
    Engine(s)
    Twin 8.1 Merc
    Posts
    719

    Re: Stern driven water pump conversion to engine driven water pump

    I personally wouldn't bypass the drive. It's used to cool it also. They get HOT. I built a drive shower for my BIII but never got to use it before I sold it.

  9. #9
    Join Date
    Apr 2016
    Location
    Houston
    Boat
    Sea Ray
    Details
    2004 280 Sundancer
    Engine(s)
    Twin 4.3 MPI
    Posts
    5

    Re: Stern driven water pump conversion to engine driven water pump

    I totally agree. I would not bypass the outdrive, I was thinking of pulling the water from the outdrive in lieu of installing a seacock.

    thanks,
    2004 280 Sundancer

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