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Volvo penta SX coupler or cone clutch went bad?

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  • Volvo penta SX coupler or cone clutch went bad?

    Hi everybody and thanks for a nice forum!

    I have had a couple of boats and last year I bought a Glastron GX185 2005 with a VP 4,3 and Sx sterndrive. Engine runs fine and the whole shot is good but there is something slipping when reaching above 3500 rpm or when doing a sharp turn and then turning back to straight. No smell in engine room for what I've felt, and I've tried with different props - still there. The boat has run at least 30 hours with the symptoms, not getting worse. Splines on crank shaft is fine and Im quite sure the prop has no caviation. Should add that I'm using the right gear lube.

    So far Im guessing on bad cone clutch or bad coupler, however, for what I've heard if coupler is bad, its reaaally bad, or does someone know if it can slip under circumstances presented above?

    Grateful for help!

    Greetings from Sweden

    /Rickard

  • #2
    something slipping when reaching above 3500 rpm or when doing a sharp turn and then turning back to straight
    Maybe the trim is to high up and prop is coming out of the water a bit
    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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    • #3
      Thanks for your answer but I have tried both with trim fully down and up a bit. Still same issue. Reaches about 34 mph at 3500 rpm and then nothing more but the engine still goes up to almost 5000 rpm. When crusing at about 25 mph (near 3000 rpm) and doing a sharp turn the boat offc goes "under surface" and when turning up to straight at about 10 mph the engine still has same rpm but does not accelerate (feels like its slipping on the clutch somehow..). Works perfectly fine if you pull of the throttle and give some throttle again.. Haven't heard about this symptoms anywhere.

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      • #4

        It it does sound like you are experiencing Ventilation, usually from being overtrimmed for a given speed. What props are you using? Any bent/twisted/damaged blades? Is the skeg on the lower unit staight, free from rough edges? Does it do it during turns both Port and Starboard. Is the area of the transom in front of the outdrive, undamaged, and free of items that may interfere with the water flowing to the drive?

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        • #5
          Cone clutches tend to grip harder as power is applied. But if they are extremely worn... The coupler, located under the water, is either one piece or sheared/broken.
          if you are referring to the coupler between flywheel and driveshaft, you would smell it if it was slipping

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          • #6
            Can't edit with iPad, and current website... so A very sharp turn will very often induce ventilation, and a lot of props do not recover when straighten out, unless power is reduced. A prop with more Rake and/Cupping might hold better and regrip sooner

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            • #7
              number one killer of cone clutches is lack of maintenance.

              either the oil level is too low or the shift linkage is not adjusted right

              however it sounds like ventilation
              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
                Ayuh,...... Welcome Aboard,....... What size, 'n pitch prop ya got on it,..??

                How beat up is it,..??

                Got any pictures,..??

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                • #9
                  Originally posted by jimmbo View Post
                  It it does sound like you are experiencing Ventilation, usually from being overtrimmed for a given speed. What props are you using? Any bent/twisted/damaged blades? Is the skeg on the lower unit staight, free from rough edges? Does it do it during turns both Port and Starboard. Is the area of the transom in front of the outdrive, undamaged, and free of items that may interfere with the water flowing to the drive?
                  Thanks for all your answers. Appreciate!
                  Regarding props I've tried with the original 21" alu 3-blade, a plastic 20" 4-blade and a 23" steel 3-blade. The 23" steel prop I tried the other day and it worked better than the other ones but werent able to try above 4000 rpm due to high waves. Good grip when turning sharp (no slip or cavitation) but starts to slip when turning to straight again until I pull of the gas, the engine stays at 3000 rpm but the boat wont accelerate until I pull of the gas and then give throttle again. Does the same at both port and starbord.

                  The sterndrive is in good condition, no rough edges or bad skeg.

                  Im wondering if it has something to do with ventilation, as you say. Could there be any cause other than overtrimmed? Such as exhaust or uneven/bad hull creating strange interference behind the boat?

                  No good pictures at the moment but Im going to the garage early this week so i can take some.

                  thanks again!

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                  • #10
                    Im wondering if it has something to do with ventilation, as you say. Could there be any cause other than overtrimmed? Such as exhaust or uneven/bad hull creating strange interference behind the boat?
                    Other things can creat issues, and pics would help maybe identify
                    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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                    • #11
                      or uneven/bad hull creating strange interference behind the boat?
                      Ayuh,..... Absolutely a possibility,.....

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                      • #12
                        Does the SX have a rubber prop hub? If so, maybe check that.
                        Summer Fling-II
                        2008 Chaparral Sunesta 264
                        Summer Fling
                        2003 Chaparral Sunesta 243

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                        • #13
                          This could be a dumb question, but does the boat stay in the water, and if so, is there any growth on the bottom that could cause this?
                          Mariah Shabah Z202 5.7L Mercruiser B3
                          Jensen Marine 1972 Cal 21 cabin sloop
                          Retired EE of 45 years

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                          • #14
                            We need a picture of the stern that shows the cavitation plate relative to the bottom of the hull/keel. Both from the back and from the side. Have the trim set in the position that you normally run the boat at.

                            Cranchi Ellipse 21
                            5.0Gi (PWTR) 1999.
                            DP-SM outdrive

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                            • #15
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                              All good suggestions to which I'll add, take a look at the gear oil and compare to new gear oil of the same type. Is it the same color? If its a lot darker, then that might be a sign of a cone clutch slipping and burning the gear oil. If it looks like new gear oil then a slipping cone clutch seems unlikely (good thing!)
                              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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