Rebuilding The Late Model Mercruiser Raw Water Pump

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by MasterFab, May 19, 2015.

  1. MasterFab

    MasterFab Active Member TECHNICAL Contributor

    Aug 17, 2010
    Wallkill, NY
    2002 340 Sundancer, Rescued, Restored, Modernized, and now Sold
    8.1L Horizons, ZF 63 V Drives
    In this post, I will describe the rebuilding of a late model, Mercruiser raw water pump. I will not describe the procedures needed to remove the pump from the engine, nor will I detail the impeller change - I am going to assume anyone considering a pump rebuild already knows how to perform these operations. The pump rebuild kit from Mercruiser includes a new shaft and bearing assembly, seals, snap ring, and a tolerance ring, under part #8M0050018 for the current pump.
    Normally, a pump will signal the need for rebuilding by leaking raw water into the bilge. It may also start to whine or groan as the bearings fail. If these symptoms manifest, I would strongly recommend you address the issue sooner rather than later, since bearing failure can be catastrophic and sudden, leaving the engine with no source of cooling water. There is also a good chance the belt will get tossed.
    So, you’ve got the pump out of the boat, and you’ve removed the mounting bracket and split the case, just as you would for an impeller change. Once the impeller is removed, the next step is pulley removal. These pulleys are pressed on at the factory with an interference fit, so you’ll need a specialty puller to remove it. If you don’t have one, many auto parts stores offer a free rental program. To provide a solid pressing surface, I thread a 3/8” - 16 cap screw into the shaft, as shown. Then, I mount the puller to the pulley, and remove the puller from the shaft.

    PDR_1026.jpg PDR_1027.jpg


    Once the pulley is off, you’ll be left with this:

    PDR_1028.jpg


    Next, take a drive punch, and carefully remove the outer seal from the housing. Tap gently all around, and be careful not to damage the housing. Don’t worry about the seal - it’s getting replaced.



    PDR_1029.jpg



    Once it is out, you’ll be able to see the internal snap ring that holds the bearing and shaft assembly in place.



    PDR_1030.jpg


    Using internal snap ring pliers, remove the snap ring. The bearing and shaft assembly should pop right out, but if there is some buildup inside the housing, you may have to tap it out gently. It’s a slip fit, so it shouldn’t take much to get it out.

    PDR_1031.jpg PDR_1032.jpg PDR_1033.jpg


    Now, look inside the housing, and you’ll see the inner seal. Make note of the seal orientation, as they only go one way, and you need to duplicate what you find. Merc has used two different seals, so take a picture if you have to. Then, take an appropriate drift or punch, and gently tap the seal out of the housing. Be careful not to nick or damage the housing in any way.
    It’s a good idea at this point to clean and paint all the parts for the housing, along with the bracket, if you have time. Otherwise, clean all the parts, dry thoroughly, and move to reassembly.
    First, lightly oil the perimeter of the new seal, and drop it into the pump housing in the same orientation you noted previously. There are instructions for seal orientation that come with the replacement parts in the kit, so follow them closely. You do need a tool to press the seal in place, and for this I use a 1.25” solid steel shaft. A piece of plastic round stock would also work, or you can use an appropriate old bearing race, but it has to be something flat, and just a hair smaller than the seal bore. Press the seal in place until it bottoms in the bore.

    PDR_1048.jpg


    Next, lightly oil the outside of the new bearings (the new bearings come already pressed on the new shaft), and also lightly oil the end of the shaft that will pass through the inner seal, and the housing interior. Just apply a very light film with your finger, not a heavy coat, then slide the new shaft into place, and carefully guide it through the seal. With just light pressure, the assembly should bottom out in the housing, exposing the snap ring groove. Install the new snap ring.

    PDR_1050.jpg


    Take the new outer seal, and apply a light coating of sealant to it, as described in the instructions. Using an appropriate mandrel or tubing, gently seat the outer seal in the housing.

    PDR_1051.jpg


    The last step is the reinstallation of the pulley. The instructions describe how to do it with a pulley installation tool, but I prefer using a press. If you do use a press, be sure to apply pressure only to the shaft, not the bearings. Once the pulley is seated, the remaining assembly of the pump is the same as for an impeller change.

    PDR_1052.jpg PDR_1053.jpg PDR_1054.jpg
     
  2. mwph

    mwph Active Member

    Jul 8, 2008
    Lake Guntersville, Tennessee River, Alabama
    1998 250 DA
    7.4L, B3
    Excellent write up. As usual. Thanks for taking the time to post.

    My first exposure to these pumps was a plastic pulley that failed & left me stranded. The rest of the pump was in perfect shape so I pressed on a new steel pulley, replaced the impeller & was back in business.

    Thanks again!
     
  3. mistercomputerman

    mistercomputerman Active Member PLATINUM Sponsor

    Jan 6, 2008
    Virginia Beach, VA
    410 Sundancer - 2001
    Twin 8.1L Mercruisers - 2009
    I am sending mine to you.
     
  4. MasterFab

    MasterFab Active Member TECHNICAL Contributor

    Aug 17, 2010
    Wallkill, NY
    2002 340 Sundancer, Rescued, Restored, Modernized, and now Sold
    8.1L Horizons, ZF 63 V Drives
    I do have a few rebuild kits in stock, so send away........

    Dale
     
  5. mistercomputerman

    mistercomputerman Active Member PLATINUM Sponsor

    Jan 6, 2008
    Virginia Beach, VA
    410 Sundancer - 2001
    Twin 8.1L Mercruisers - 2009
    I actually replaced mine with Hardin SS pumps.
     
  6. Almightys

    Almightys Member

    195
    Jun 15, 2015
    Warren, MI
    1992 Sundancer 330, 7.4l's w vdrives, and genny
    454 Mercs
    So is this essentially the same process for the older Gen that ran the mechanical fuel pumps?
    Have any of those rebuild kits in stock?
     
  7. MasterFab

    MasterFab Active Member TECHNICAL Contributor

    Aug 17, 2010
    Wallkill, NY
    2002 340 Sundancer, Rescued, Restored, Modernized, and now Sold
    8.1L Horizons, ZF 63 V Drives
    In stock, I have two remaining shaft/bearing rebuild kits, enough for a boat with twins, but the supply for them is relatively abundant, so if you need your water pumps done, send me a PM. I don't have anything in stock for fuel pumps.

    Dale
     
  8. Almightys

    Almightys Member

    195
    Jun 15, 2015
    Warren, MI
    1992 Sundancer 330, 7.4l's w vdrives, and genny
    454 Mercs
    Just an FYI and bump. This was super easy and cheap to rebuild. It cost me $80 for new bearing and seals for both pumps. I bought two new fuel pumps off amazon for $95 and then the Sierra pump rebuild kit for each pump for $90 for both. So for approx $270 I completely rebuilt both pump with new fuel pumps vs $600 ea if you go the mercruiser way to buy new. Even if you lack some tools, harbor freight coupons are awesome.
    This thread on the Baja forum shows the steps to disassemble/assemble and has part no to take to your local grainger or motion industries for parts
    http://bajaboatowners.com/threads/2784-How-to-Rebuild-your-Mechanical-Fuel-Sea-pump-Assy
     
  9. rondds

    rondds Well-Known Member SILVER Sponsor

    Oct 3, 2006
    Jersey Shore
    2001 380DA
    Merc 8.1s (2008)...Hurth ZF 63 V-drives...WB 7.0 BCGD (2013), Garmin 8208 & 740 MFDs, GMR 24xHD dome
    UGH. Thanks for reminding me. Impellers this spring :-(
     
  10. rondds

    rondds Well-Known Member SILVER Sponsor

    Oct 3, 2006
    Jersey Shore
    2001 380DA
    Merc 8.1s (2008)...Hurth ZF 63 V-drives...WB 7.0 BCGD (2013), Garmin 8208 & 740 MFDs, GMR 24xHD dome
    UGH. Thanks for reminding me. Impellers this spring :-(

    Thanks for the "How-to" Dale! My grandfather had a press in the basement to maka-da-vino. Will that work?
     
  11. Happy Hour IV

    Happy Hour IV New Member

    294
    Nov 22, 2009
    California
    340 Dancer 1988
    454 Merc BW V drives
    I am looking forward to my next maintenance on my 454 pumps. Just finished converting to crank mounted.
    Also during the process i replaced all 4 oil coolers but moved them to the top of the engines in the process.
    Norhing left at the bottom except for bilge pump. Trying to figure out how to move it up now.
    I suspect it will stay as is.
     
  12. rondds

    rondds Well-Known Member SILVER Sponsor

    Oct 3, 2006
    Jersey Shore
    2001 380DA
    Merc 8.1s (2008)...Hurth ZF 63 V-drives...WB 7.0 BCGD (2013), Garmin 8208 & 740 MFDs, GMR 24xHD dome
    HHIV, I'd like a photo doc of that pump conversion! Helped a friend change impellers on his Crusaders. What a breeze!
     
  13. Bugsy24

    Bugsy24 Active Member

    Jun 25, 2010
    Freehold, New Jersey
    2008 310 Sundancer
    T-350 Mag,Br3's W/Axius
    Thanks Dale..... Wink Wink Nod Nod!
     
  14. Bob & Sue

    Bob & Sue Active Member

    Jun 3, 2011
    Browns Point Tacoma WA
    Sold 1999 270DA Sundancer
    5.7l Mercuiser
    Great post thanks taking the time to document the process, I've been thinking about rebuilding my spare pump and replacing the pulley it has a small chip on one side.
     
  15. dpmulvey

    dpmulvey New Member

    Dec 19, 2007
    Homeport: Charles City, VA
    1999/2007 330 Sundancer Hardtop.
    6.2 Merc Horixons
    1.5:1 Velvet Drives
    +1. I wonder about the air bleed systems.
     
  16. Happy Hour IV

    Happy Hour IV New Member

    294
    Nov 22, 2009
    California
    340 Dancer 1988
    454 Merc BW V drives
    so a couple of you guys asked for the photoblog of my crank conversions and cooler relocates. I did not keep an ongoing log so
    I took some 95% complete pictures. Still need to do some hose supports, painting and hose clamp cleanup but you can get the idea from the pictures. Basically gutted the raw water system, all hoses, coolers, some oil lines and the pump. Installed the crank pump, new coolers to the top of the engine and reworked water hoses.

    https://dl.dropboxusercontent.com/u/107812872/20160329_094018-min.jpg

    https://dl.dropboxusercontent.com/u/107812872/20160329_094025-min.jpg

    https://dl.dropboxusercontent.com/u/107812872/20160329_094038-min.jpg
     
    Last edited: Apr 3, 2016
  17. dpmulvey

    dpmulvey New Member

    Dec 19, 2007
    Homeport: Charles City, VA
    1999/2007 330 Sundancer Hardtop.
    6.2 Merc Horixons
    1.5:1 Velvet Drives
    Way to go HHIV..... Yours is how "BOATERS" want to see it done factory. Please show your improvements to SR/Merc. Maybe..."just maybe" they will listen.....nah, won't happen.
     
  18. saopm

    saopm Member

    762
    Oct 6, 2010
    North Fork - Long Island, NY
    2007 340 Sundancer
    Mercury 8.1s Inboards
    Do the raw water pumps need to be primed in any way after changing the impellers over the winter? The strainers to the pump are completely dry. The only thing I can think of is to open one of the drain plugs on the pump once I'm floating to let the air out. Let me know if this is worthwhile or if I'm just over thinking again.
     
  19. Bugsy24

    Bugsy24 Active Member

    Jun 25, 2010
    Freehold, New Jersey
    2008 310 Sundancer
    T-350 Mag,Br3's W/Axius
    Hey Dale, going in this week if the weather cooperates!

    Unknown.jpeg
     
  20. boatrboy

    boatrboy Active Member

    Oct 3, 2006
    Orange, CT
    1999 270 Da
    7.4 MPI w/B3
    Dale,
    I have pulled apart a spare pump from a 1999 bravo three with 7.4 mpi motor. I had to press everything apart due to salt water getting into the bearings. I have cleaned and painted everything (outside) but the new bearings seem tight and I'm not sure what is supposed to be the press fit. Are the pumps like mine assembled the same as your write up and I press the new bearings onto the shaft? This would mean that the bearings in the housing should slip in.
    I used an old cylinder hone to clean the bearing bore but the bearings don't seem to slide in so before I bring these to my shop, I wanted to verify if they are indeed supposed to be a slip fit.

    Thanks,

    Mark
     

Share This Page

Show Sidebar