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New to me boat, melted exhaust

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  • New to me boat, melted exhaust

    Hi there, I'm reasonably new to the boating scene. Had a 1990 bayliner that I just sold, and purchased this 1997 Bluewater mirage with the 5.7l volvo penta/sx cobra out drive. The boat is pretty darn clean and in good shape..other than some crispy looking exhaust. The manifolds/risers look good. But just past them where the rubber couplers begin, and the y-pipe are looking like they got pretty hot at one point. I've got a small drip on the port side upper coupler. The boat doesnt overheat on the muffs, the oil is clean, and the plugs are all equally rich looking. I've included some pictures. Obviously I'm looking at replacing the couplers at least. What else would you guys recommend looking into? The motor has 425 hrs and has only been in fresh water. I'm going to replace the impeller as well. Thank you

  • #2
    Sounds like a good place to start (impeller). Make sure that the outlets of the elbows are not clogged. I would probably take those aluminum exhaust pipes and re-paint them. If it had exhaust flappers (Volvo discontinued them past a certain year) they will be vaporized laying in the bottom of the exhaust housing, or hanging off the pin that they ride on. If you have them they will be at the top of the Y pipe when you take the burnt exhaust hoses off.
    If they are melted off they will be in the bottom of the exhaust housing & you will have to pull the drive to get them out. I had that happen on my Cobra once.
    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"

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    • #3
      Without further investigation I would say the motor overheated. Most probable cause would be failure of the water pump impeller. The issue is how bad did it over heat. The boots looked to have been replaced (or at least from my angle) and this is just paint peeling. If its just paint then just needs repainting
      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"

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      • #4
        Here's what the flappers look like. If you have em, there is a V/P TSB that tells you to remove them and not replace.
        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


        • #5
          Originally posted by Lou C View Post
          Here's what the flappers look like. If you have em, there is a V/P TSB that tells you to remove them and not replace.
          I'm curious Lou. I thought these are a must have to keep back waves from flooding hot exhaust valves. I could see where VP may have work-around on newer models. But removing them from older exhausts..?? Do you know their reasoning?
          '96 Larson 174 SEI BR. 4.3LX 4 bbl Weber s/n 0F786604. Alpha One Gen II s/n 0F709315

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          • #6
            My pal forgot to retighten the clamp on his PS cooler after winterization and it blew open. He finally shut down when his alarm went off. Much smoke when he opened his hatch. Things got so hot his trim hoses melted open, and his drive water impeller was cooked crispy. He's lucky that trim oil didn't catch fire. We pulled his engine two years later for another repair, and surprisingly his flappers were intact.
            '96 Larson 174 SEI BR. 4.3LX 4 bbl Weber s/n 0F786604. Alpha One Gen II s/n 0F709315

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            • #7
              start with the impeller. lack of cooling water does not take long to burn the exhaust hoses and burn the paint off the y-pipe.

              FYI, the rubber hoses should have been replaced. the rubber burns at 250F, paint melts about 300F

              however pull them to see if the inside is burned

              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

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              • #8
                Originally posted by harringtondav View Post

                I'm curious Lou. I thought these are a must have to keep back waves from flooding hot exhaust valves. I could see where VP may have work-around on newer models. But removing them from older exhausts..?? Do you know their reasoning?
                Not so much a work-around as it was testing. VP did testing on back flow ingestion and decided the problems with flappers outweighed the chances of water flowing back into the engine. The main thing is to slow down and idle for a bit after cruising. If you go from high speed immediately to neutral idle, or off, you'll run a greater risk.
                2007 Seaswirl 210 BR
                Volvo Penta 5.0GL-H and SX-A
                Aerial Airborne tower
                Perfect Pass Stargazer

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                • #9
                  Thanks for all the input! Going to start working on it this weekend. Definitely pulling the impeller first, and pull off the couplers. Are the couplers pretty much the same lower and uppers? Here's a pic of the boat to keep things interesting 😁

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                  • #10
                    look at the parts breakdown. simply go to the store side of the iboats page, follow the link for genuine volvo penta parts and it will take you to the volvo penta parts breakdown.
                    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

                    Comment


                    • #11
                      look at the parts breakdown. simply go to the store side of the iboats page, follow the link for genuine volvo penta parts and it will take you to the volvo penta parts breakdown.
                      Thank you

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                      • #12
                        Originally posted by harringtondav View Post

                        I'm curious Lou. I thought these are a must have to keep back waves from flooding hot exhaust valves. I could see where VP may have work-around on newer models. But removing them from older exhausts..?? Do you know their reasoning?
                        Well I can say this:
                        V/P simply adopted OMC's transom design when they went into the joint venture era that produced the SX drives. So after some time they came to the conclusion that the flappers can melt during an overheat and clog the exhaust. I being a salt water boater, have had to replace the exhaust every 5-7 years to avoid manifold failure and water in cyls. So I have seen these flappers up close often. And my take on it is that as long as you don't have a bad overheat they work. Never had water in a cyl in my OMC. So not sure why Volvo went away from it but they eventually changed the exhaust exit on the SX drives that may have eliminated the need for those flappers. One thing I noticed every time I remove the exhaust was that both flappers were in the open position. So maybe Volvo in their testing found that they really don't stop backwash. If that's what they found then their decision is logical.
                        What I'd do...is just replace them (as I did after my bad overheat back in '13) or you could, remove the exhaust bellows...and fit an inboard style exhaust flapper right over the exhaust exit in the transom mount. This would eliminate the flappers in the Y pipe but still provide back wash prevention just as any other inboard boat has. Simple, elegant solution.

                        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


                        • #13
                          I think VP eliminated the need for the flaps by increasing the height of the risers.
                          Summer Fling-II
                          2008 Chaparral Sunesta 264
                          Summer Fling
                          2003 Chaparral Sunesta 243

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                          • #14
                            Finally got a chance to work on this thing today. Pulled the risers and exhuast bellows. There are no flappers to be seen, just the pins they used to ride on. Is the flapper itself plastic? Or did someone previously remove them? Only one small wire bundle got burnt, maybe the trim sender (guage not working)? Going to pull the impeller now. I think maybe the belt broke going to the fresh water pump, as there are 3 new belts on this thing, and 2 aren't even tight!

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                            • #15
                              Sign up today
                              there was a TSB to remove the flappers.

                              your exhaust hose is burnt.... buy new
                              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

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