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Mercury 40hp gear and throttle set up

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  • Mercury 40hp gear and throttle set up


    I have just purchased my boat and outboard. On first run the throttle lever was acting as the gear lever and the gear lever was acting as the throttle lever.
    We achieved about 5 knots!
    Wworth bearing in mind that previous owner had never ran the boat.

    I have reversed the cables as someone suggested at the linkage and the throttle is not working lovely with the engine getting up to good revs.
    The prblem now is that the gears are not engaging in forward or reverse so the boat won't move.

    There is some slack in the cable.

    Doe sthe linkage just need to be adjusted to take up any slack?

    Help would be appreciated.

  • #2
    Re: Mercury 40hp gear and throttle set up

    Remove the engine cover and have someone move the throttle lever. If the throttle linkage is moving the cables are configured correctly. You do not adjust "linkage" on the engine for either the throttle or gearshift. You adjust the trunion on the cable. The trunion is the barrel on the threaded portion of the cable. Cables are adjusted by disconnecting them at the engine. While holding the throttle linkage against the stop (fully closed) bring the cable end up to the attachement point. If it does not line up exactly with the attachment point, adjust the trunion so it does. Repeat for the shift cable making sure the shifter and the engine shifter are in neutral (spin the prop to verify). That's all the adjustment there is. If there is still slop in the cables, something is wrong with the control box or cables.


    • #3
      Re: Mercury 40hp gear and throttle set up

      many thanks. with the cable disconnected can you manually adjust the gear so that it is in neutral? do you just press it with your finger and check the prop to see if it freely spins?
      once adjusted and connected at this point i trust the shifter will do the rest?

      does same apply for throttle ie after adjustment in neutral the shifter will take the engine to its maximum?

      many thanks for all your help


      • #4
        Re: Mercury 40hp gear and throttle set up

        thanks for the help. i have followed your guide lines. the shifter is interconnecte. at a certain point when moving the throttle the gears move as well. the shifter needs to be dropped right back to change the gear.

        the only problem now is that in reverse gear you can give it full throttle but in forward gear you can only give it a little and then it goes into neutral. I would understand if that was happening in reverse as the shifter may be designed so you can not give it to much throttle in reverse???


        • #5
          Re: Mercury 40hp gear and throttle set up

          You need to understand that props provide their "push" going forward. In reverse, the prop runs backwards and they are terribly inefficient. Throttle opening is indeed limited in reverse as well.

          Now then -- If the engine seems to go into neutral as you apply more power, it is very probable that you have what is called a spun hub on the prop. The hub of the prop is secured to the blade area of the prob by a rubber cushion. That cushion is bonded to the hub and the blade area. If the bond breaks, the hub simply slips inside the blade area under power. You can check this by placing one mark on the hub and another directly in line with it on the blade area. Run the engine until the slippage occurs. Now see if the two marks are still aligned. If not, the hub has spun. If they are still lined up, something else is wrong.


          • #6
            Re: Mercury 40hp gear and throttle set up

            many thanks.

            In reverse the throttle can be applied from fast to slow.
            In forward the throttle can be applied slightly and then it goes in to neutral and you can physically se the lever arm move from forward into neutral.

            the shifter is of a design wher the throttle is linked to the gears. Not knowing it could be the trunions et up


            • #7
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              Re: Mercury 40hp gear and throttle set up

              many thanks can you just confirm that low revs lies between the 2 throttle stops. 1 way being reverse rev, the other being forward rev?