Changing water pump impeller 7.4

Discussion in 'Sport Cruisers' started by Slowboat, Jun 15, 2020.

  1. Slowboat

    Slowboat New Member

    16
    Jun 30, 2019
    2000 340 sundancer
    7.4 MPI mercruiser/ V drives
    I am changing the impeller on our 2000 340 with 7.4,s. Any advice would be appreciated from past experience.

    Thank You
    Slowboat
     
    Chris-380 likes this.
  2. northern

    northern Well-Known Member

    Jan 17, 2007
    West coast Vancouver to Alaska
    380 Aft Cabin 1989 GPS and Charts by Nobeltec
    Twin 454 strait shaft
    I have a spare pump. I swap out the existing pump with the new one then change the impeller on the one I took out. I do this because water pumps fail and if you do not have a spare it can be a long way home on one engine. To change the impeller in place is a lot of work. So you land up taking it out so a spare is a quick and simple solution.
     
  3. Slowboat

    Slowboat New Member

    16
    Jun 30, 2019
    2000 340 sundancer
    7.4 MPI mercruiser/ V drives
    Northern, thank you. Is charging out the complete pump a major job. It looks like a tight place to reach.
     
  4. Stee6043

    Stee6043 Well-Known Member

    Jun 1, 2015
    West Michigan
    1997 Sundancer 400
    7.4L Gassers
    I took a crack at impellers on my 99 340 before paying the marina to do it. I'm still not sure what kind of sorcery they use to get behind those engines...
     
  5. Slowboat

    Slowboat New Member

    16
    Jun 30, 2019
    2000 340 sundancer
    7.4 MPI mercruiser/ V drives
    Thank you STee6043. This is what I was thinking. Looks like it would be easier to pull the motor. I appreciate your comments.
     
  6. Stee6043

    Stee6043 Well-Known Member

    Jun 1, 2015
    West Michigan
    1997 Sundancer 400
    7.4L Gassers
    For what I ended up paying...it's possible that's what they did. ha.
     
  7. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Ha! Sorry... didn't mean to laugh :)

    Wrestle the water hoses off... remove the belt... remove the three screws holding the bracket to the engine... bring entire setup to your workbench. Various combinations of socket extensions and wrenches. Most importantly, while my description sounds simple - and the actual process is - you'll be doing some of this only be feel... and as noted, access is "challenging" ;)
     
    QT1 and Caveman22 like this.
  8. northern

    northern Well-Known Member

    Jan 17, 2007
    West coast Vancouver to Alaska
    380 Aft Cabin 1989 GPS and Charts by Nobeltec
    Twin 454 strait shaft
    It is not fun job. If you do it mark one hose on the water pump and what port on water pump it came from, mark one of the three bolt locations holding the pump to the bracket and same on pump and UP arrow on water pump. Then transfer marks to new pump. The bolts holding the pump together are different lengths make sure to put them all back in same place. I take lots of cell phone pictures of any thing I do on boat before I start work that way I can figure out how it goes back together. If it has not been done recently hoes will be very stuck to pump. Once you remove rad clamps use channel lock plyers to twist hose back and forth to break the bond. Once loose see if you can get hose off when pump is still attached to engine. There is a lip on pump that old hoses hang up on. I use a small pry bar to force the hose off. Have beer available upon completion. It takes me about an hour.
     
  9. Slowboat

    Slowboat New Member

    16
    Jun 30, 2019
    2000 340 sundancer
    7.4 MPI mercruiser/ V drives
    Boat for sale. Lol. I will give it a go. Patients is the key.
    Great information.

    Thank you
     
  10. bone354

    bone354 Member

    160
    Oct 3, 2007
    Great South Bay NY
    2000 340 Sundancer
    454 Horizon V Drives
    Remove the rears seat and you can prop the engine cover all the way up so you can stand up. If you have log exhaust you can pop the two inside exhaust tubes off to give you even more room. I put a Tyrap around top hose of pump so you don't mix them up. I do it like Lazy days and remove the bracket with the pump still attached. The one bolt is behind the fresh water (antifreeze) hose that goes on circulating Water Pump. You can probably get it but it was pretty hard to get bracket out with hose on. I drop antifreeze and have a wet vac going do it doesn't go overboard. Not sure if there is a way to get antifreeze out another way and reuse. I just add new. pay attention to the bolts on pump and leave the old impeller in old housing so you know which way to spin new cover onto new impeller so blades are going right direction. Put a little grease or some kind of lubricant on housing. Just start all the bolts till they all catch then tighten. After you have it all back together when you are filling the antifreeze back up there is a bleeder valve you can open to get air out as your filling. Once antifreeze comes out you tighten it back up and fill it all the way up. Bleeder valve is on top of engine behind heat exchanger right in middle of thermostat housing. I am sure there is other ways to do this but this seems to be the easiest way to me. Good luck its not that bad.
     
  11. rcknecht

    rcknecht Well-Known Member

    Mar 23, 2009
    toms river,nj
    340 Sundancer 2001
    T 454 MPI
    you guys are making this too hard... I just changed mine on Monday... 1. Shut the RW intake, and loosen the serpentine belt tensioner. 2. Remove the clamps the hose leaving the strainer, and the clamps on hose going into the Trans Cooler 3. remove the clam on the AF hose leaving the HE that covers the nut on the bracket holding the pump. (the is a nut on the top and bolt on the bottom of the bracket. All of the AF will drain out... You will need two gallons of AF when your done. 4. remove the bracket. 5. remove the four nuts holding the pump to the bracket. 6. Pull out the pump and bracket, with the hoses. 7. Attached your new pump (use a complete hot swap with the pulley) Make sure you look at an attach it the same way... BTW I grease the new impeller before install. 8. Push the hoses under the engine. The RW hose goes under the transmission. 9. Pump and bracket in place, you may have pull your hoses. 10. Attached the top nut to the bracket and attach the pump to the bracket. 11 put the belt back on, check it to see if you need to replace it first. 12. tighten the bolts. 13. put all the clamps back on. 14. Reattach the AF hose, and fill the HE.
     
  12. bobeast

    bobeast Dance the Tide SILVER Sponsor

    Oct 22, 2017
    Isleton, CA
    2002 310DA
    350 MPI w/V-drives
    I like that idea. I've definitely found it easiest to just pull the pump. Having a pre-prepped spare to rotate in will just make it easier still.
     
    Caveman22 likes this.
  13. britandy

    britandy New Member

    16
    Aug 19, 2019
    340 Sundancer 2000
    Mercrusier 7.4 MPI, inboard, V drives
    No need to remove the antifreeze hose that sits in front of the top bracket bolt. The hose is flexible enough that you can, with a bit of force, get a small/short socket on the bolt with a long extension.
     

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