Announcement

Collapse
No announcement yet.

Forward gear disengaged at about 2500-3000 RPM

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Forward gear disengaged at about 2500-3000 RPM

    Any thought about this? I was just cruising back toward the harbor and jumped out of gear, it did shift back into gear and I "limped" in. The shift cable was just replaced. Also when I throttled down the engine died, then wouldn't stay running at lower rpms. After I docked I moved the shift linkage at the engine R-N-F and back a couple of times, engine then started and idled perfectly. Nothing seemed to be loose by the engine cable linkages. Has shift interrupt system (I would appreciate a good link to information about this system).

    #2
    Year and make of engine/drive would be helpful. Sounds like it may not be adjusted properly. BTY did the shifter move? how did you shift back into gear, return to neutral and then into forward?
    1997 Maxum 2400 SCR 5.7LX Bravo II

    Mike

    Comment


      #3
      G Rob, is this the Herculbunteir stern drive, or the Cowengluskei stern drive?

      Although I suspect that you have a Merc A drive, the model would be helpful!
      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


        #4
        OMC Cobra 7.5L. Don't know if the shifter moved but it must have, I just shifted back into gear, I also shifted out of gear and into reverse, then back to forward. Good news is the marina pulled it today to go over the shift cable adjustment.

        Comment


          #5
          If the shifter moved then you need to increase the drag on it by turning in the drag set screw.
          1997 Maxum 2400 SCR 5.7LX Bravo II

          Mike

          Comment


            #6
            OK..... 7.5L engine and OMC stern drive.
            Rob, is this a King Cobra, or a cone clutch King Cobra ?
            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


              #7
              Rick,
              King Cobra, dog clutch.

              Comment


                #8
                Originally posted by G ROB View Post
                Rick,
                King Cobra, dog clutch.
                Think of the stern drive dog clutch engagement teeth (not the hypoid gear teeth) as though they are dove-tail cut.
                Most are cut as to engage in one direction of rotation only (the load side), and to slip or ratchet in the other direction of rotation (the coast side).
                The engagement side of the dove-tailed teeth are incline cut (ramped for lack of a better term) so that they remain engaged while under load.


                Below is an example of a dog clutch sliding sleeve and it's counter-part, the "driven" gear.
                (either "driven" gear (FWD or REV) powers the sliding sleeve when engaged, of which in turn powers the propeller shaft)

                Note the slight incline cut to the dog clutch teeth (red lines).
                When engaged with the counter-part dog clutch teeth, they form what could be considered a dove-tail configuration.



                Click image for larger version  Name:	merc dog clutch sliding sleeve.jpg Views:	0 Size:	56.6 KB ID:	536452

                Once these teeth engage, they will remain engaged until:
                ...power is reduced.
                ...over-water speed exceeds the prop thrust speed.
                either requiring the sliding sleeve to become disengaged from the driven gear.



                If your dog clutch drive is coming out of gear while under power, you may have very worn dog clutch teeth along an unwanted force (shift linkage) that wants to separate the two.
                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


                  #9
                  Thanks for the information Rick, I'll recall these images when I run it next. Marina went over the cable they just installed and I should be back in the water. Sea trial when weather permits. How much would you suspect the ball detents?

                  According to everything I've read about this drive they are notorious for eating gear sets if the shift cable adjustment isn't maintained. Any thoughts about what happens when the cable isn't adjusted properly?

                  Comment


                    #10
                    ....................
                    Originally posted by G ROB View Post
                    Thanks for the information Rick, I'll recall these images when I run it next. Marina went over the cable they just installed and I should be back in the water. Sea trial when weather permits. How much would you suspect the ball detents?
                    Well, I have some experience with the Merc A drive dog clutch, and quite a bit of experience with motorcycle transmission dog clutch engagement.
                    However, other than understanding how the dog clutch system works, I do not know enough about the Cobra system!


                    According to everything I've read about this drive they are notorious for eating gear sets if the shift cable adjustment isn't maintained.
                    Yes, I understand that as well.

                    Any thoughts about what happens when the cable isn't adjusted properly?
                    Apparently you nailed it above.

                    My suggestion for those who are having OMC Cobra issues, is to replace the OMC Cobra with the VP SX or DP-S drive via the conversion kit.
                    No more ESA, no more finicky ESA adjustments, no more finicky shift cable adjustments, no more dog clutch issues, no more two shift cables, etc.


                    That said, there are lots of OMC Cobra owners who are very happy with their drives.
                    They have either found a good Cobra tech to work on and service them, and/or have learned how to keep them adjusted correctly themselves.
                    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

                    Working...
                    X