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Penta sx-m clutch slipping in forward

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  • Penta sx-m clutch slipping in forward

    Hi all,
    looking for help with my 2004 sx-m paired with a 4.3 gxi. I just bought this with 180 hours on it...and soon had issues were it would rev high and clunk when shifting into forward. Reverse works fine. I verified the shift cable is moving the selector on the outdrive, and even adjusted it to where it fully buries the shift selector cam in the forward position...as it had a tiny bit more it could go. I also changed the oil for volvo synthetic. Rpms are around 750...and I don't see that as an issue since reverse grabs perfect. It has gotten worse very quickly..to the point where I can't use the boat. If i am under load and I back off the throttle but stay in gear, it now loses connection and slips. I never dreamed a volvo with 180 hours would have a bad cone clutch but I am convinced at this point.

    I've briefly looked into this and feel my best option is a used upper...but im having trouble finding the sxm in a 1.6 ratio for under 1500. The rebuild cost is unbelievable....from what I understand there are special tools and shimming involved when replacing clutch. I've heard of shimming the shift arm and also lapping the cones..but heard that is just buying time. I'm very disappointed with the whole ordeal and was looking for some suggestions and recommendations.

  • #2
    Ok well I popped off the shift mechanism and manipulated the clutch with my finger while turning the prop. Reverse is definitely WAY more grabby then forward. Forward slips quite a bit. I can tell it is glazed. Has anyone tried lapping the cone on an sx-m? I read that there is a special coating on the clutch and you can't lap this one. I also saw a service bulletin that changes the clutch to a different part number. I would love to drop a new clutch in but the shimming and shim tools are discouraging me. I can't understand why the shimming would change since the clutch floats and doesn't affect the gear stack up. Why can't I crack the case..drop in a new clutch,keep track of the shims..put it back together in same order and go on my way?

    Comment


    • #3
      You’re correct about not needing to reshim for a clutch replacement. If you don’t misplace any of the shims.

      I highly recommend lapping the gear cups when you do, because I’ve seen other mechanics either just replace the clutch or lap the old clutch and reuse it. They have a little bit better than 50% success rate doing it this way.

      Here are some tips that I use to get an almost 100% success rate.
      Order a new clutch, you will use the old clutch to do the lapping and discard it when done.
      Check forward and reverse gear backlash before and after the repair. You want them to be the same. And remember that where you place the dial indicator on the gear tooth will affect the reading, so make sure you get it in the same place both times.
      You will need the tool to remove the lower gear, because after lapping the gears and bearings need a very very good cleaning to remove ALL the lapping compound. Use water based lapping compound.
      Follow the Volvo service bulletin on how to lap the cups. This is important, you don’t just spin the clutch in the cup.
      Use the correct Volvo service manual so you know where all the shims are, and make sure they go back in the same place and same order as they came out.
      Mark the upper and lower gears so they go back in the same place.
      Good Luck Muc

      Comment


      • #4
        Thanks muc. I did assume I would be lapping the cups with the old clutch and putting a new one in..just in case the old one has lost some metal. I did plan on buying the wrench to pull the lower gear..no way I'm risking compound in the gear case. I will check lash before and after. I have both the seloc and volvo service manuals...although the Volvo one is 10x more helpful. I have seen a service bulletin with a new pn for the clutch but have not seen one with the lapping procedure. I assume I can find this in the Volvo database with my serial number?

        Comment


        • #5
          Originally posted by Sfwjesse View Post
          I assume I can find this in the Volvo database with my serial number?
          No. Volvo has recommended against lapping for many years. It was last allowed during the 270 - 290 drives. So that’s where you should look.

          Good Luck Muc

          Comment


          • #6
            Another alternative to lapping the cone clutch parts is to glass bead blast them. This was passed on to me from a Volvo tech instructor years ago.
            Kenner, Louisiana 1980 Donzi 18'. 2+3 6.2 MPI Alpha 1

            Comment


            • #7
              Originally posted by kenny nunez View Post
              Another alternative to lapping the cone clutch parts is to glass bead blast them. This was passed on to me from a Volvo tech instructor years ago.
              Never heard of that one. I would think it would be tough to get the uniform finish that's required.

              The service bulletin for Lapping of engagement sleeve and cones is.
              Group Number Version
              44–1 13 01
              Good Luck Muc

              Comment


              • #8
                So I've looked high and low and I'm striking out on the lapping bulletin. Does anyone know the cliff notes version? Muc I know you said you can't spin the clutch...I'm assuming it's a back and forth twisting motion for a certain number of degrees with some amount of pressure...but is there more to it?

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                • #9
                  So ive found other writes ups on cone clutches for yanmar drives that talk about using 280 grit lapping compound and doing 5 turns in either direction. I'm think I'll start there and use common sense to just break the glaze and not go too crazy. My other thought is I definity should check the shimming on the shift mechanism to ensure it's pushing in far enough...as that could be why it failed to begin with. I also noted that volvo released a bulletin where they say to remove the spring on the clutch.. which coincidently pushes the clutch away from the forward gear. Those two items could contribute to less contact between the cup and cone and allow partial slippage at low load which would promote glazing. I could be off base here but it makes sense to me.

                  Comment


                  • #10
                    I'm not sure how Yanmar clutch's work ---- never worked on one ----- but I do know that MerCruiser and Volvo cut their cones and clutch's differently to allow them to disengage. Basically what often works for one doesn't work for the other. So I don't think following Yanmar's procedure would be best for you.

                    Due to copyright I can't post the entire bulletin, but here is some of it.

                    The proper way to do this is to:
                    A. Coat the gear cup with a thin even layer of medium valve grinding
                    paste.
                    B. Insert the engagement sleeve into the cup and rotate approximately 30°
                    back and forth using as much pressure as possible for about 10 times.
                    C. Lift engagement sleeve straight up and rotate it 120° (1/3 turn) and
                    repeat the above procedure.
                    D. Lift engagement sleeve once more straight up and turn it another 120°
                    (1/3) and repeat the above procedure.

                    There is more about how to tell when you have achieved uniform contact.

                    I really recommend you get a copy of the service bulletin. Maybe ask the people you got your parts from or a Volvo dealer. Any authorized Volvo dealer has access to this S.B.
                    Good Luck Muc

                    Comment


                    • #11
                      Thanks muc. I bought my parts online so I'm not sure how much response I would get with a bulletin request. I gonna try a local dealer..but i am really striking out on volvo in my area..nobody wants to work on them and noone seems to know anything. I did the lapping per above and got a uniform contact and a haze in the metal all the way around...but I still see some shine.....might be my 280 grit isn't aggressive enough but I don't want to overdo it. The new clutch is def more of a matte finish then my old one on the forward side...so hopefully alot of my slippage issue was there.

                      I do have service bulletin p-44-1 18 01 that tells me the new clutch part no and states to not put the spring back in...but it also states new clutch must mate with clutch shoe 3856502. I can't tell if my original shoe is this part. It's very frustrating to not have all the info but I guess I'm gonna run with my shift shoe and see what happens

                      Comment


                      • #12
                        Originally posted by Sfwjesse View Post
                        Thanks muc. I bought my parts online so I'm not sure how much response I would get with a bulletin request. I gonna try a local dealer..but i am really striking out on volvo in my area..nobody wants to work on them and noone seems to know anything. I did the lapping per above and got a uniform contact and a haze in the metal all the way around...but I still see some shine.....might be my 280 grit isn't aggressive enough but I don't want to overdo it. The new clutch is def more of a matte finish then my old one on the forward side...so hopefully alot of my slippage issue was there.

                        I do have service bulletin p-44-1 18 01 that tells me the new clutch part no and states to not put the spring back in...but it also states new clutch must mate with clutch shoe 3856502. I can't tell if my original shoe is this part. It's very frustrating to not have all the info but I guess I'm gonna run with my shift shoe and see what happens
                        I would get rid of the shine. Or try this ---- its what Volvo recommends.
                        Apply thin even layer of Prussian blue marking paste or equivalent in the gear cup. Insert the
                        engagement sleeve and rotate under pressure back and forth, no more than 10°. Remove (straight up)
                        engagement sleeve from cup and inspect both pieces for uniform contact. If uniform contact is not
                        obtained repeat above described procedure as many times as needed.

                        I would be worried about mixing shifter parts. Had one come into the shop that somebody had done that. Wasn't pretty.

                        If you post the serial number, I can try to research and maybe tell you if you need more parts.
                        Good Luck Muc

                        Comment


                        • #13
                          Serial no 4202089842. Did another round of lapping and they look 10x better..nice even haze now all the way around

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                          • #14
                            Here is what the cups looked like before:

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                            • #15
                              Sign up today
                              And here is where i have them at now:

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