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    Vibration question!-gctid403771

    Good evening. it's been a while since I've been to this board to help with problems (that's a good thing though!!! ).

    We were up on the the Pacific Ocean (near Tofino, British Columbia) this past week. Boat running well. Lots of improvements and new things over the past couple of years. All good!!! Fishing ok, companions delightful, weather good.

    But, then when I'm starting to feel a bit smug, we were running offshore and I picked up (rather suddenly) a pretty good vibration. We immediately drop off the RPMS and it gets lot better, but I can still feel it. I quick phone call to my friend, Rick, and his first thought was a dinged prop. Per his suggestion, I changed to a spare prop that is perfect. Unfortunately, no improvement. We made a decision to continue our fishing trip as things seemed to work okay at slow speed (I also do have a kicker motor that we could use in case of complete failure). Over the next few days, we put 25 hours (mostly at trolling speed - 650 rpms) and some at displacement speed (2000 RPMs @ 7 MPH), but no fast planing work at all. Not getting worse.

    Since that point, I did a little more diagnosis work and here's a list of some other facts:

    Last year, I put in a rebuilt transmission (upper unit). This included new bearing crosses. I also pulled the engine and replaced Primary Drive Shaft (pds) bearings last year too. I've also kept that cavity well greased too. I also replaced the Borg Warner coupler that bolts on the flywheel.

    When I had it up on the trailer yesterday, I checked the drive dipstick and oil was good. I also opened the bellows and saltwater poured out (yikes - thats not so good). :sorrow:

    So, I'm kind of leaning towards some kind of problem with the Ujoints (crosses). I am taking the prop to a prop shop tomorrow to have it checked and balanced, but I'm pretty sure it is ok.

    We do have another trip coming up offshore in a week, so I have limited time to diagnosis and/or fix. The boat is on the trailer up there (British Columbia), but I have lots of room to work on it in the parking lot when we go back.

    So, my question to you helpful people is actually two-fold:

    1) Do you think we'd be okay just running it at slow RPMs for another week (approximately 80 hours on the meter)?

    2) if not, what's your best guess? (Ujoints/crosses, lower unit bearing, transmission (again), or something else).

    Thank you for your thoughs,

    ~markb

    Oh, yes, the details that everyone always want: 1985 2655, AQ260A engine, V/P 270 drive.

    #2
    If salt water is in the bellows and it's already causing a vibration you need to do crosses, PDS and bellows again. I am sorry. I wouldn't run it.You could do all that work in less than a day.

    Comment


      #3
      If your joints are already bad it could fail at any moment. A failure it that area can do alot of damage. Engine rpm and moving parts can fly around and the cause alot of damage and even sink the boat. I wouldnt run ot but thats your call.
      1989 Avanti 3450 Sunbridge
      twin 454's
      MV Mar-Y-Sol
      1979 Bayliner Conquest 3150 hardtop ocean express.
      Twin chevy 350's inboard
      Ben- Jamin
      spokane Washington

      Comment


        #4
        If your joints are already bad it could fail at any moment. A failure it that area can do alot of damage. Engine rpm and moving parts can fly around and the cause alot of damage and even sink the boat. I wouldnt run it but thats your call.
        1989 Avanti 3450 Sunbridge
        twin 454's
        MV Mar-Y-Sol
        1979 Bayliner Conquest 3150 hardtop ocean express.
        Twin chevy 350's inboard
        Ben- Jamin
        spokane Washington

        Comment


          #5
          Mark, I just now saw your thread.

          Doubt that PDS bearings would have failed this soon, nor that the bearing crosses would cause a problem this soon.

          Long shot here..... but look to see if all of the trunion bearing cap C clips are all still in place.

          I've never seen one missing, but never say never.

          Attached files [img]/media/kunena/attachments/vb/707559=30049-Bearing cross caps clips.jpg[/img]
          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

          Comment


            #6
            Hey Rick - - I will take a look and see if the clips are all there. I'm leaning towards replacing the ujoints/crosses. Can I do this with the drive transmission still attached? or would it be easier to remove the upper unit/transmission and slide the whole assembly off of the PDS splines?

            LOL - you may remember that I have a LOT of experience with that step from last year.

            I mentioned that there was salt water inside the bellows, so at a minimum that should be replaced too (I'm figuring), so for that particular thing, I'll surely have to pull the whole shebang off anyway.

            thx,

            markb

            Comment


              #7
              Well, we were back up in BC for another week on the water. As long as I had it out 'on the hard', I took along some parts and did some replacing. Here's what I did:

              1) Replaced the Ujoints/bearing crosses. As Rick suggested, the old parts didn't look bad, but I went ahead and replaced anyway. It was an easy (and fairly cheap) step.

              2) I also re-installed the newly repaired and balanced propeller.

              3) Discoverd that the bellows were pretty crappy (several holes), so replaced with new bellows.

              4) added more grease to the pds cavity - enough to force a little water (and lubricant) rear-ward - I could see it oozzing out a little when looking at the splines (with the ujoints off).

              5) changed the oil in the leg. It was pretty milky.

              6) checked the plugs in the engine. all look good - no abnormal wear. pretty sure it is NOT an engine issue anyway - engine is running wonderfully.

              7) In neutral, I cannot sense any vibration (both at idle and at 4,000 - 5,000). But might not be noticeable because it isn't under load in neutral.

              Bottom line - vibration still present. We used the boat all week (95 hours), but just went slow. Most of it was trolling, but also some long-term cruising at 2,200 rpms (8mph). The vibration still there. Didn't get any worse.

              At this point in the POE (process of elimination), it would seem to me there are two likely candidates left: 1) some problem in lower unit (e.g., thrust bearing), or 2) PDS bad.

              I have an extra lower unit laying around here (it's from a 4 cylinder, so the wrong ratio); I think I will bolt this (other lower unit) on and see if the vibration is still there. If so, then I guess the next step is pull engine and check out PDS.

              Sound reasonable?

              ~markb

              Comment


                #8
                I don't like the water in the PDS area. If water sat in there for some time it could have toasted even fresh PDS bearings, but....you can usually hear them even in neutral. If its only when in gear and you have milky oil I would guess something is not happy. What I have seen in alot of drives is water gets in oil, then separates and ruins the bearings in the lower unit(water is heavier and separates into the bottom of the drive), and also forms condensation which wreaks havoc on the upper transmission bearings which are not submerged in oil.

                I have a 280 drive in good shape for a V-8 if you find yours is too far gone, located in Bellingham.

                Comment


                  #9
                  Mark, the rear PDS bearing is an unlikely candidate since these were replaced so recently....., but as said.... never say never.

                  Have you check for prop shaft run-out?

                  Your spare 280 lower unit prop shaft can be used for a replacement without the need for any re-shimming.

                  All shim control is done via the shim control area behind the angular contact bearing and within the prop shaft bearing carrier.

                  IOW, if all parts go back in just as they were removed, nothing to the gear pattern changes on this style lower unit.

                  Great time to replace the two seals as well.

                  .
                  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

                  Comment


                    #10
                    Can you point me to a link that talks about how to check prop shaft runout? If it's "off", does that mean the shaft itself is 'wonky'? or the bearings that hold the shaft?

                    Also, when you talk about replacing the two "seals", you're talking about the seals immediately forward of the propeller . . . right?

                    mark

                    Comment


                      #11
                      bratzcpa wrote:
                      • 1 wrote:
                      • Can you point me to a link that talks about how to check prop shaft runout? If it's "off", does that mean the shaft itself is 'wonky'? or the bearings that hold the shaft?
                      • Also, when you talk about replacing the two "seals", you're talking about the seals immediately forward of the propeller . . . right?




                      mark
                      • 1 wrote:
                      • You'd place a dial indicator on the prop shaft and spin it.

                        Allowable run-out is in the .003" range.
                      • Correct! These are inside of the aluminum prop shaft bearing carrier, and are not accessible until the carrier is removed and the prop shaft is removed from the carrier.



                      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

                      Comment

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