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    Engine coupler?-gctid385838

    1989 Bayliner 2556, 5.7 OMC, Im getting a rythmic rapping when in gear from behind the bell housing, Increases with RPM's..Im thinking coupler..Can that be replaced with out removing the engine from the boat..Any suggestions or ideas for pinpointing the problem?

    #2
    The noise could be you gimbal bearing or u-joints. They can be replaced by pulling the drive. If it is your coupler the drive will have to come off, and the engine will have to at least be pulled out and up enough to access the coupler.

    Pull the drive first and rule out or change out the gimbal bearing and u-joints. If the coupler is going out you might be able to tell if the input shaft from your drive has aluminum shavings in the spline grooves.

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      #3
      +1 on the u-joints or gimbal bearing. Have you greased the gimbal bearing (zerk on stbd side of transom assy., outboard.)?

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        #4
        Thanks for the help...I put the outdrive on 4 weeks ago for the season...the gimbal and ujoint looked good..no rust, bearing smooth as silk, ujoints nice and tight no play. I greased everything.. I was confident that they were very good.... I put a screw driver to the bell housing then my ear and it seems like the sound is coming from there...but who really knows...Gimbal bearings im told are usually a growling noise espically when you load them up by turning the wheel....heres my question...if I remove the outdrive and the sound goes away...is it because there is no load on the coupler anymore...or am I still in the dark on excatly what it is.... diagnosis is 75% of the problem the other 25% is making the problem go away...I would hate like hell to remove the engine only to find no issue with the coupler..and the problem was else where..pulling the outdrive I guess would be the first step though since its the easiest...that way I would get to see the ujoints and gimbal bearing maybe one of them let go...any suggestions

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          #5
          chris wrote:
          Thanks for the help...I put the outdrive on 4 weeks ago for the season...the gimbal and ujoint looked good..no rust, bearing smooth as silk, ujoints nice and tight no play. I greased everything.. I was confident that they were very good.... I put a screw driver to the bell housing then my ear and it seems like the sound is coming from there...but who really knows...Gimbal bearings im told are usually a growling noise espically when you load them up by turning the wheel....heres my question...if I remove the outdrive and the sound goes away...is it because there is no load on the coupler anymore...or am I still in the dark on excatly what it is.... diagnosis is 75% of the problem the other 25% is making the problem go away...I would hate like hell to remove the engine only to find no issue with the coupler..and the problem was else where..pulling the outdrive I guess would be the first step though since its the easiest...that way I would get to see the ujoints and gimbal bearing maybe one of them let go...any suggestions
          Pulling the drive and running the motor (make sure you can run coolant to the motor) will take the u-joints, gimbal and coupler all out of play, so if you still hear the noise it is something other than those components. Yes, gimbal bearings do tend to growl when going bad especaily with the boat in a high speed tight turn.

          Yes I think pulling the drive is your next step. Check out the u-joints very carefully for any slop. It will be difficult to inspect the gimbal bearing very closely as it will be inside the gimbal assembly. When was the last time they were replaced? If you don't know, you may want to go ahead and change them out and see if that solves your problem before you pull the engine and have a look at the coupler.

          There may also be something amiss inside the drive itself.

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            #6
            If you only hear the noise when the drive is in gear (both FWD and REV) but it's quiet when in neutral, I would think there's something happening in the outdrive. I had a similar issue with my '05 Bravo 3 - turned out one tooth sheared off of one of the driven gears in the lower housing and caused a TON of collateral damage. Entire gear set was destroyed. Fortunately I was able to get an entire new drive from Merc under warranty. I would recommend that you or your mechanic drain the gear lube and check for metal shavings. If you see some, further disassembly of the lower unit is called for. Good luck!
            Ted
            2005 288 Command Bridge
            350 Mag MPI / BRAVO III

            Every Day Is Saturday

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              #7
              Ill keep you all posted..thanks for the help...heres something to ponder.....why doesnt sombody redesign the bell housing so it is a 2 piece unit, that has a lower half and an upper half..this way you could unbolt the upper and inspect the coupler and repair if necessary without removing the engine...im hoping its the ujoint or gimbal bearing...is there a way to drive the gears on the outdrive when it is off?

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                #8
                Do any of you know if the 1989 omc cobra 5.7 has a flex plate? Could it be that?

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                  #9
                  I once had a rythmic rapping (more like a dull, knocking sound) noticeable at idle, about 4 "knocks" per second. I ultimately had to replace the drive (BIII) due to sheared teeth (good insurance!!). Hope you don't have to go through that though.

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                    #10
                    chris wrote:
                    Do any of you know if the 1989 omc cobra 5.7 has a flex plate? Could it be that?
                    No flex plate here.

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                      #11
                      chris wrote:
                      heres my question...if I remove the outdrive and the sound goes away...is it because there is no load on the coupler anymore...or am I still in the dark on excatly what it is....
                      Answered here in 2859er's post.

                      2859er wrote:
                      Pulling the drive and running the motor will take the u-joints, gimbal and coupler all out of play, so if you still hear the noise it is something other than those components. Yes, gimbal bearings do tend to growl when going bad especaily with the boat in a high speed tight turn.

                      Check out the u-joints very carefully for any slop.

                      There may also be something amiss inside the drive itself.
                      Ditto!

                      Saturday288 wrote:
                      If you only hear the noise when the drive is in gear (both FWD and REV) but it's quiet when in neutral, I would think there's something happening in the outdrive.
                      Possible, but this would be limited to within the prop shaft area.

                      With the Cobra Dog Clutch drive, all components are rotating when the engine is running (Gimbal bearing, universal drive shaft, bearing crosses, two upper gears, vertical shaft, three lower unit gears)

                      The only component not yet rotating, would be the sliding sleeve and prop shaft until a gear is selected.

                      This is why the Merc A drive sea water pump is vertical shaft driven and is always spinning when the engine is running.

                      chris wrote:
                      Do any of you know if the 1989 omc cobra 5.7 has a flex plate?
                      You mean like a Borg Warner coupler?



                      NO..... your engine has a rubber hubbed drive coupler similar to the Mercruiser coupler.



                      .
                      Rick E. Gresham, Oregon
                      2850 Bounty Sedan Flybridge model
                      Twin 280 HP 5.7's w/ Closed Cooling
                      Volvo Penta DuoProp Drives
                      Kohler 4 CZ Gen Set

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                        #12
                        Boat coming out of the water tomorrow...Gonna pull drive...I have a feeling its the coupler..Are sierra couplers just as good as OMC. Any opionions? on that or heavy duty ujoints and gimbal bearings...brands?

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                          #13
                          IMO go with the good stuff it is worth the extra cost for these critical parts. You don't want them to fail and you don't want to replace them before you have to. When I replaced my coupler I went with the stainless steel as opposed to the aluminum one (Merc). Not sure if you can get an OMC compatible stainless steel coupler but if you can I recomend it.

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                            #14
                            Best plave to buy Genuine OMC parts? Id like to go to one place and get it all ujoints, coupler and GB

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                              #15
                              Boat out of the water today...GB was fine...ujoints mint..its either in the lower unit or the coupler...Ill keep you all posted

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