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Flushing 5.0L Gi engines in wet slip with block drain hoses, is there a better way?

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  • Flushing 5.0L Gi engines in wet slip with block drain hoses, is there a better way?

    We are new to this boat and the previous owner used this flush system to run freshwater through both 5.0L engines after returning to the slip each time. We wanted to keep up the routine, but the block drain is a very small opening and we weren't sure if we could plumb those lines to another water port on the engine that could flush better, maybe on the thermostat housing? Or...

    The old owner rigged up hoses and a Tee so he can flush both engines at the same time, but the parts are hokey and I'd at least like to do a better job or newer hose parts. Any ideas are appreciated.

  • #2
    Probably need to see what you have, and need to post some more before iboats will let you upload pics. Using a 3rd party place to like pics would help for now

    Not much flushing is done with the block drains, my first thought is the original owner might have used them to drain the slat out before flushing with fresh, don't know right now
    94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
    95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
    07 Seadoo GTX
    Merc Adults Only VP Adults Only
    G-Dad always said "First Liar doesn't stand a chance"


    • #3
      I think it is a factory arrangement from reading other forums, on the port engine it is also where the water heater connects one of its hoses to the block drain. There is a Tee there to allow the flush hose to connect too. Then the previous owner added a garden hose Tee between both flush hoses to each engine so he can fluch both at the same time through a hose run to an access hole above the swim step.

      Here are some pics, the port block drain has the brass Tee to connect the water heater and the starboard block drain just connects to the drain hose:

      You can see what a small, like 1/4" NPT", hole it is, so I am not sure how much flushing water gets through or how long I should be flushing for. Some say that it won't get past the thermostat, but I assume some does before it cools to close.
      Last edited by Monterey296Twin5.0Gi; January 21st, 2020, 05:33 PM.


      • #4
        The water heater on my Formula was connected the same way, just the flush doesn't look like it would work very well, but just my opinion

        Many use a Tee connection on the intake hose to the pump and switch then start the motor.

        For others to see a few pics easier

        Click image for larger version

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        94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
        95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
        07 Seadoo GTX
        Merc Adults Only VP Adults Only
        G-Dad always said "First Liar doesn't stand a chance"


        • #5
          I would invest in two neutrasalt injection systems from volvo, then add their flush kit.
          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

          Past Boats
          1970 Wooster Hellion - Merc 9.8
          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

          What’s behind you doesn’t matter.Enzo Ferrari


          • #6
            Thank you both for the help,

            I just discovered the Neutra Salt system that they sell.

            Would I need one kit for each motor? Or can I "Tee" the hoses and just inject twice as long?

            Do you know where it plumbs into on the engine?


            • #7
              The flush needs to be before the raw water pump. This way you can run the engine .
              Engine is only to be run at idle rpms while on the hose
              Now on the nutrasalt system. If you don't boat in saltwater it's a waste of your money.

              Last edited by Thalasso; January 22nd, 2020, 12:11 PM.
              Assault Squadron NINE
              River Assault Division NINETY-ONE-1966


              • #8
                I should specify the boat sits in a saltwater slip, so we need to be able to flush in water.

                Thank you, I think I might get the parts to at least move the flush hose IN from the block drain on the side up to Tee off of the intake hose on the raw water pump. I see they descipe doing that here:

                MOD EDIT

                Can you explain if there is also a pump/impeller in the sterndrive? I am a little confused as I thought there was one in the sterndrive, also the raw water pump running off belts at front of engine, and also the Chevy-style water pump front/center of the engine. Do I have that right, 3 pumps?
                Last edited by GA_Boater; January 22nd, 2020, 08:32 PM.


                • #9

                  I'm in Minnesota so I don't know much about flushing. (Mercury tells me that our lake water is better than the tap water in some parts of the U.S.) but the kit I posted a link to is the one that customers who "winter" in FL. (and have their boat transported south) have me install on their new boats. Don't know if that one is the right size for your engine --- check with whoever you buy from to make sure.

                  No Impeller in Volvo drives.
                  Most garden hoses have barely enough water flow to do one engine much less two.
                  The flush hoses that you have now was Volvo's 1st attempt. The photo with the blue cap is their 2nd attempt. Note that the blue cap MUST be tightened with a wrench.
                  I'm told that Nuetra-salt is better than nothing, but not as good as a proper flush. A proper flush takes at least 15 minutes.

                  Good Luck Muc


                  • #10
                    My last boat had a similar system. It basically had two water lines from a T connector entering the engine block on both sides at the flush port. Water from the tap entered both sides of the block and pushed the block and riser water out the drive of the boat. It was not designed to allow the engine to run during this time as it totally bypassed the water pump and intake.
                    Summer Fling-II
                    2008 Chaparral Sunesta 264
                    Summer Fling
                    2003 Chaparral Sunesta 243


                    • #11
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                      You could of course just take the intake hose off the inlet side of the raw water engine driven pump...stick a hose down it and run it for a minute or so.