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Volvo Penta 5.0 GXI-G Riser problem.

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  • Volvo Penta 5.0 GXI-G Riser problem.

    Hey all,

    I'm looking for some help with an overheating problem. I have a 5.0GXI-G in a 2007 Glastron 259 GS.

    A few weeks ago, my temperature gauge alarm went off while I was out on the water and I opened up the engine compartment and found that pretty much everything was very hot to the touch. So I shut everything down and got towed back in.

    Since then, in an effort to troubleshoot the over heating, I've checked all the hoses, replaced the water pump (even though the old one seemed to be working fine) and then replaced the risers and manifolds. I just bought the boat this year so I don't know when the last time the risers / manifolds were changed but it looks like they were pretty old. They were blocked up pretty good.

    Now that I've done all of that, the engine temp seems to be running perfectly. I have an IR temp gun and have temped pretty much everything in the compartment. The boat seems to be running really well, but when it idles, or I'm cruising very slowly in a no wake zone, the starboard riser temperature shoots up. Then when I give it gas and get up on plane, it cools back down again. Then I back down the throttle and it heats right back up again. At idle, it gets as high as like 195 degrees. On plane it comes down to between 120 and 130. It's always hotter at the base of it where it meets the manifold and the manifold itself is usually around 20-30 degrees cooler directly below where it meets the riser. And the outside of the manifold where the water comes in stays consistently around 110 no matter how many RPMs I'm at. So it certainly seems like water is coming in, but then I have no idea what's happening. I've started the boat with the hoses from the thermostat housing to the manifolds disconnected and there seems to be plenty of water flowing.

    I know that one side will generally run a little hotter than the other but this is different. The port riser seems to be working fine. Sits between 110 and 135 depending on the RPMs.

    However, that's not always terribly consistent. That's how it is most of the time but today I started the boat at the dock and within 10 minutes or so, the port riser was at about 165 and the starboard riser was around 180. Then I revved the engine to about 1500 rpms and they both cooled down to around 130. Then when I backed it down to idle, the port riser stayed cool (around 120) but the starboard one started to climb again and within a few minutes it was up over 165 again. But interestingly, the temp of the exhaust elbows that connect to the back of the risers always seem to stay constant at around 115-120.

    I'm running out of ideas here. Any help would be greatly appreciated.

    Thanks a lot.

  • #2
    Is there a thermostat installed and is it functioning correctly?

    Your not moving enough water and/or you have an air leak.
    Get a piece of clear tubing, a double barbed fitting and clamps. Remove the hose going to the thermostat housing from the water pump and install the tubing.

    Run it in the water and see if you see bubbles
    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"

    Comment


    • #3
      The thermostat is installed and functioning. I tested it in a pot of water.

      I'll give the clear tubing a shot. But if I had an air leak somewhere before the thermostat housing, why would it affect only one riser and not both?

      Comment


      • #4
        Water flows the path of least resistance, one is always hotter then the other. If air is getting in then there is less water flowing. At idle your not getting enough to keep the motor cool. Speed increases and pressure also increases but still is not enough based on heat being generated
        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"

        Comment


        • #5
          Right. I suppose one riser only gets any water at all once the other has "gotten its fill".

          Comment


          • #6
            So I tried the clear tubing. The water is running perfectly. No bubbles at all. I took off the thermostat housing and inspected that again. Cleaned it out a bit just in case but it looked perfectly fine. Then I took off the hose that runs from the housing to the manifold and inspected that, and the fitting that connects it to the manifold. Both were good. Ran a garden hose through them and then reconnected it to the thermostat housing and ran it quickly with it disconnected from the manifold and it pumped really well. Then I tried crimping off the port side hose about 50% to restrict flow to that side to see if it would send more water to the starboard and nothing. The port riser started to climb pretty quickly but the starboard side didn't cool at all.

            So as far as I can tell, there isn't a problem with water flowing to the manifold. Something is either happening inside of them, or the flow is blocked on the way out???

            The strange thing is that the riser is really hot at the bottom (170), pretty hot at the top (150-160) but much cooler right where it connects to the elbow (like 120). It just seems to be the main vertical part of the riser that's heating up for some reason.

            Comment


            • #7
              about the only thing left is the cooling passages inside the manifold and elbow (what you're calling the riser is actually an elbow) you might have to drain the water out of the manifold and remove the elbow and see what it looks like. Here's what a VP style manifold looks when new....you may be getting clogging on one side and that makes all the water go to the other side. I have the same style exhaust on my OMC and the elbow runs at about 95* at idle and the hottest they get is 125-135* measured right after coming off plane.
              Click image for larger version

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              1988 Four Winns 200 Horizon
              4.3 OMC Cobra

              98 Jeep Grand Cherokee 4.0 Selectrac
              07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

              "While air doesn't freeze....rust never sleeps"

              Comment


              • #8
                Then I tried crimping off the port side hose about 50% to restrict flow to that side to see if it would send more water to the starboard and nothing. The port riser started to climb pretty quickly but the starboard side didn't cool at all.

                The strange thing is that the riser is really hot at the bottom (170), pretty hot at the top (150-160) but much cooler right where it connects to the elbow (like 120). It just seems to be the main vertical part of the riser that's heating up for some reason.
                Along the same line as Lou, might have the wrong gasket installed on the starboard side
                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"

                Comment


                • #9
                  I've removed it a few times now to inspect it. They're brand new and they look perfectly clean from what I can see. And I used the gaskets that came with them which is the same one that's on the port side which is working properly. I'm considering swapping the port and starboard risers to see if the problem stays on the starboard side or if moves to the port side. Then I'd know if it was a problem with the actual part and not the flow.

                  Comment


                  • #10
                    Have you looked down the Y pipe to see if there is a clog ?
                    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"

                    Comment


                    • #11
                      Try this first:
                      disconnect the feed hoses at each manifold, hook up a water hose to it and turn it on. Then go to the back of the boat and compare them individually. Do they both flow the same amount of water out from under the transom mount and exhaust bellows?
                      1988 Four Winns 200 Horizon
                      4.3 OMC Cobra

                      98 Jeep Grand Cherokee 4.0 Selectrac
                      07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                      "While air doesn't freeze....rust never sleeps"

                      Comment


                      • #12
                        Well the boat is in the water so I have no idea how much water is coming out the back. And accessing the Y pipe is pretty tricky since it's buried in behind the engine. I've done all the work on it in the water but now that I'm starting to suspect a blockage behind the riser and manifolds somewhere, I might need to pull it. It was just much easier to run tests on it while it was in the water.

                        Comment


                        • #13
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                          If your exhaust does not have a riser extension between manifold and elbow, you can remove the elbow and boot and look down the exhaust Y pipe
                          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"

                          Comment

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