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4.3L mount failure scenarios

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    4.3L mount failure scenarios

    I have a 4.3L in my 2003 185. I assume the mounts are similar to automotive mounts in that if they collapse the engine drops. Wouldn't that break the coupler? So even if you checked alignment twice a season you're still just one random mount failure away from a coupler failure? Or is there some other mechanism I'm not seeing that keeps this from commonly happening.


    Curious how common coupler failures are.

    -Robert


    #2
    While a collapsing mount won't "break" a coupler, it will cause rapid wear due to the side load on the splines. This is a good reason to periodically check drive/coupler alignment as coupler replacement usually means pulling the engine.
    2007 Discovery 246
    300mpi BIII
    Welcome island Lake Superior

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      #3
      Every boat mount i have seen are solid studs with a nut on bottom passing through block mount, then nut on top. They arent a rubber cased mount like automotive. Cant see any way they could ever fail. I think a stringer would rot and pull out before the mount would
      1993 formula pc 31 twin 454 bravo 2
      1989 2655 cierra 5.7 omc cobra
      2014 "searay" tandom trailer

      Anchor bay clinton river
      Michigan

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        #4
        Originally posted by businessgetmoney View Post
        Every boat mount i have seen are solid studs with a nut on bottom passing through block mount, then nut on top. They arent a rubber cased mount like automotive. Cant see any way they could ever fail. I think a stringer would rot and pull out before the mount would
        +1
        I don't see how this is possible. If anything minor changes may occur over time and you should be checking the alignment each time you pull the outdrive off for maintenance. On the other hand, having gone through that just recently I can tell from experience that a perfectly aligned engine/drive improves engine performance.

        Good luck
        Retired, computer expert / executive
        Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
        Live in the Bay Area, CA, USA, boat in Turkey
        D-Marin @ Turgutreis in Bodrum/Turkey
        bdervisoglu8@gmail.com
        bulent@pacbell.net

        Comment


          #5
          Engine mount failure, if it happens is most often collateral to some other event. Like has been said, when the drive is off for service, check the alignment. I had a pair of 4.3’s on my previous boat. In the 15 years I used them I never had to adjust the alignment. The only problem I had with the gen 2 alphas was the ujoint bearing caps were not properly lubricted before installation, no zerk permanently lubed style, and they had to be replaced after 900 or so hours.
          P/C Pete
          Edmonds Yacht Club (Commodore 1993)
          1988 3818 "GLAUBEN
          Hino EH700 175 Onan MDKD Genset
          1980 Encounter Sunbridge "Misty Blue" (Sold)
          MMSI 367770440
          1972 Chevrolet Nova Frame off Resto-mod in the garage
          Boating on the Salish Sea since 1948

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            #6
            Originally posted by businessgetmoney View Post
            Every boat mount i have seen are solid studs with a nut on bottom passing through block mount, then nut on top. They arent a rubber cased mount like automotive. Cant see any way they could ever fail. I think a stringer would rot and pull out before the mount would
            Oh that 4.3is special. My 90 has those fluid filled mounts. Something to do with vibration abatement. They don’t look the strongest for sure. Mine are backed up with slightly over length cables with balls or slugs on both ends threaded through plates, one on each side. I recall GM having a similar loop style rig in response to powerful V8 mills snapping motor mounts. I guess they kept they kept engines from wandering too far, tugging on throttle linkages and sending people for a wild ride.

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              #7
              Thanks for all the responses! Any recommendations on where to get the alignment tool? I see a lot out there with a lot of variability in price. Some come in kits with tools to replace the bellows and gimble but I'm not assuming I'll need those.

              -Robert

              Comment


                #8
                It is a simple, splined hub. The one I had used had a T-sghaped handle bar for easier use but that is not essential. Look at the attached video. The idea is to be able to insert/remove the tool in/out without needing to apply too much pressure in either direction.

                https://www.youtube.com/watch?v=x-g6fFYtDLw

                Good luck,

                Retired, computer expert / executive
                Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
                Live in the Bay Area, CA, USA, boat in Turkey
                D-Marin @ Turgutreis in Bodrum/Turkey
                bdervisoglu8@gmail.com
                bulent@pacbell.net

                Comment


                  #9
                  The mount base is insulated from the stud with some type of rubberized urethane, yes they do wear down over time.
                  Dave
                  Edmonds, WA
                  "THE FIX"
                  '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                  (.030 over-Vortec top end-part closed cooled)
                  The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                  Misc. projects thread
                  https://www.baylinerownersclub.org/f...56-gctid789773

                  Comment


                    #10
                    Is this $32 + free shipping alignment tool too good to be true? Are there good and bad versions of the tool?


                    https://www.ebay.com/itm/Alpha-Bravo...!US!-1&vxp=mtr

                    -Robert

                    Comment


                      #11
                      Looks just like the one I use.
                      Dave
                      Edmonds, WA
                      "THE FIX"
                      '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                      (.030 over-Vortec top end-part closed cooled)
                      The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                      Misc. projects thread
                      https://www.baylinerownersclub.org/f...56-gctid789773

                      Comment


                        #12
                        You could make one on a lathe. Probably take about an hour by the time you machined it and cleaned up. Easily worth $100 if you farmed it out. So to me, this is a good deal at thirty bucks.
                        2007 Discovery 246
                        300mpi BIII
                        Welcome island Lake Superior

                        Comment


                          #13
                          Should the tool have splines on the end? These don't. How do they fit into the coupler?

                          -Robert

                          Comment


                            #14
                            No splines needed, it fits into the ID of the coupler splines.
                            Dave
                            Edmonds, WA
                            "THE FIX"
                            '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                            (.030 over-Vortec top end-part closed cooled)
                            The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                            Misc. projects thread
                            https://www.baylinerownersclub.org/f...56-gctid789773

                            Comment


                              #15
                              No! It should have splines. The whole point of the alignment tool is for it to act as the horizontal shaft from the drive unit going into the coupler. It should be an exact image of the horizontal shaft, in terms of number of splines, their thickness, etc. As you insert the alignment tool, it will go deeper and deeper into the coupler and if the coupler and the gimbal bearing are perfectly aligned there won't be any friction around their inner surfaces and the tool will go in/out easily. Otherwise, the tool will go into the coupler at a slight angle and friction will make it harder to insert or retract. That is how you can tell if alignment is good.

                              Good luck
                              Retired, computer expert / executive
                              Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
                              Live in the Bay Area, CA, USA, boat in Turkey
                              D-Marin @ Turgutreis in Bodrum/Turkey
                              bdervisoglu8@gmail.com
                              bulent@pacbell.net

                              Comment

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