Replacing circulating pump on 8.1 w/v-drives

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by boatrboy, Feb 3, 2023.

  1. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    I noticed on one motor a drop of antifreeze in the water pump weep hole so while I have the mufflers out I’m going to replace them.

    For those who have changed these, do I have to remove the crossover tube or can I lift the water pump into the special seal on the bottom of the crossover tube while it’s still on the block?

    Any other words of wisdom while doing this?

    Thanks in advance.
     
  2. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    Anybody?

    Also - are Sierra pumps inferior to the Mercruiser circulator pumps?
     
  3. Bill Curtis

    Bill Curtis Well-Known Member

    627
    Mar 24, 2022
    Eastern NC
    '95 220 Overnighter
    454 Mag. Bravo3 w/ 2.0:1 ratio gears and 28 pitch props
    454 Mag Bravo3. 2.0:1 ratio gears w/ 28 pitch props
    IMHO... If it was my job, I would do the crossover, too. That whole assy looks to be a job for a contortionist. Make it as easy as possible to get everything aligned properly and sealed to avoid problems later.

    On the quality, I would say any major named marine circ pump is GTG. Stainless internals and back cover are main concern. I stay away from the no name Chicom knockoffs.
     
  4. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    I am lucky right now to have a lot of room as my mufflers and mounting plates are off. I figure I’ll change the pumps now while access won’t get any better:)
    I have already cleaned the rust stains ;).... An will be changing the raw water impellers while in there.

    upload_2023-2-7_9-15-8.jpeg upload_2023-2-7_9-15-8.jpeg
     
  5. BillK2632

    BillK2632 Well-Known Member SILVER Sponsor

    Jun 25, 2009
    Lake Norman, NC
    2014 Cobalt R5
    Volvo Penta V8-300 DP
    I've never changed one on an 8.1, but did on my 4.3 and 5.0's. I used a Sierra on my 4.3, it was still working fine 10yrs later when I sold it. One other tip, loosent the bolts on the pulley before you take the belt off.
     
    Nater Potater likes this.
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx 502 mag
    2005 Baja 242 islander 496
    502 mpi Bravo 1
    496 mag B1
    It's a closed cooled system so doesn't need to be SS. GM would probably be half the price and the pump looks like the one on my PU truck with the 8.1.
     
  7. Bill Curtis

    Bill Curtis Well-Known Member

    627
    Mar 24, 2022
    Eastern NC
    '95 220 Overnighter
    454 Mag. Bravo3 w/ 2.0:1 ratio gears and 28 pitch props
    454 Mag Bravo3. 2.0:1 ratio gears w/ 28 pitch props
    Boy, does a pic change the landscape. That change out will be easy. And the circ pumps are std everyday ones with black paint, since it is FWC. I dream of work space like that
     

    Attached Files:

    Nater Potater likes this.
  8. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    This is what has me stumped. The merc pumps are ~$300 +, the sierras are ~$130 and I did not price out the auto ones yet.
    I wonder what would cause the merc ones to be so much more?

    I figure while I’m in here I’ll change the thermostat and need all the special seals on the crossover pipe. It just doesn’t stop adding up….

    I’m glad I’m doing all of this myself.
     
    Nater Potater likes this.
  9. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx 502 mag
    2005 Baja 242 islander 496
    502 mpi Bravo 1
    496 mag B1
    Merc uses the gm pump and marks it up a bit for profit.:eek:. Stay away from Chinese knock offs.
     
    Nater Potater likes this.
  10. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    I thought about your note and pulled the pump off today on one side. It has the GM cast number on it and decided to check places that sold GM factory parts. Everyone I looked up shows this parts “discontinued”. Hmmm so is the Sierra part a Chinese knock off?

    E6F79932-A911-4870-9D48-294F0EDBF212.jpeg
     
  11. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx 502 mag
    2005 Baja 242 islander 496
    502 mpi Bravo 1
    496 mag B1
    Sierra is a solid co.
     
  12. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    This is crazy - no one has these (Sierra) in stock and no delivery expected dates…

    I even called the Chevy dealers and they state only re-mains available for these for gm vehicles.

    I may end up paying twice the amount to get the Mercruiser ones :(
     
  13. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx 502 mag
    2005 Baja 242 islander 496
    502 mpi Bravo 1
    496 mag B1
    you could just replace the bearing and seal.

    Autozone $130 lifetime warrantee

    01-07 GMC 2500 8.1
     
  14. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    Scoflaw - the fine print excludes marine use on the warranty.

    I just pulled the original apart and the impeller is in fact brass or bronze and the back plate is stainless. None of the auto ones offer this option. I did not find a bearing or seal kit for this yet, and I’m not sure how it all presses together anyway (front to back or back to front). Now I don’t disagree that since it’s fresh water cooled sitting in antifreeze probably won’t kill it, but I wonder why did merc engineers this it to be important? Maybe because the environment is salt (in my case)?

    I talked to one vendor and he assures me the Sierra one is made in China, but really don’t know if that is a fact.

    I ordered all the seals for now and pulled the heat exchanger to see if there were any barnacles - but it was clean as a whistle to my surprise.

    Anyone else replace one of these pumps on a 8.1 yet and what brand did you use?

    17CE6F7B-DE6C-4856-B809-12FB6C1C2952.jpeg
     
  15. Bill Curtis

    Bill Curtis Well-Known Member

    627
    Mar 24, 2022
    Eastern NC
    '95 220 Overnighter
    454 Mag. Bravo3 w/ 2.0:1 ratio gears and 28 pitch props
    454 Mag Bravo3. 2.0:1 ratio gears w/ 28 pitch props
    The marine pumps are always bronze / Stainless, as they are intended for both raw water and closed cooling. Yours is closed cooling (antifreeze coolant - not raw water), just like a truck, so the ordinary truck one will work.

    Automotive ones say not for marine use because raw water (salt or brackish) would eat them up in short order. Your pump won't see raw water.
     
    Nater Potater likes this.
  16. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    I bit the bullet today and ordered two Sierra pumps after finding someone who had two in stock finally.

    Hopefully they are made well.

    Also repaired the single point air escape barb that broke off the back of that device on the back of the raw water pump. It appears to be only an air escape for when you pump up the drain system and I’m guessing that the hose that “goes nowhere” is there to keep dirt out of the chamber where the piston rides during draining. I tapped and insert a barb fitting to attach the hose. What the heck, it’s winter and I have time ;)
    4A3266EE-AE00-4EE8-8CFD-2C4C532544F2.jpeg
     
  17. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    This project did not go as planned but this should not have shocked me.
    As mentioned above I purchased everything I was touching pulling the pumps which included all seals, short hoses and thermostats. The only thing I decided to leave alone was the crossover tube. I decided to just replace the tube seal and install the water pump “up and in” to it. We that did not work out. The bolts that hold the seal won’t budge so I ended up removing the crossover pipe and bring it home where I immediately snapped the bolts:mad:.
    Looks like the pipe is coming to work with me to get drilled out…

    12A80902-24B0-47B1-8E6D-9034A0B29647.jpeg 1452E423-8181-4CDA-8464-DA5DB76847F2.jpeg
     
    Nater Potater likes this.
  18. Nater Potater

    Nater Potater Well-Known Member GOLD Sponsor

    Oct 19, 2020
    Southwest Idaho
    1992 300DA Sundancer
    Twin Merc Alpha I Gen II I/O's with 5.7 V8's
    What a pisser!
     
  19. boatrboy

    boatrboy Well-Known Member

    Oct 3, 2006
    Orange, CT
    2006 340 Sundancer
    Twin 8.1 Horizons with V-Drives
    Well today I was lucky enough to have one of our R&D technicians mount it in a Bridgeport and drill it out. It was so corroded that he had to drill bigger and Heli-coil it. I'm back in business now but waiting on those darn expensive gaskets from the Crossover to the block.
     
    KevinC and techmitch like this.
  20. Bill Curtis

    Bill Curtis Well-Known Member

    627
    Mar 24, 2022
    Eastern NC
    '95 220 Overnighter
    454 Mag. Bravo3 w/ 2.0:1 ratio gears and 28 pitch props
    454 Mag Bravo3. 2.0:1 ratio gears w/ 28 pitch props
    Oh, what it must be like to have direct (free) access to and R&D lab with all it's nifty toys......

    Can only fantasize.
     

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