Johnson 55hp (1979) Idle Screw Not Returning - Could it be a worn cable?

I have a Johnson 55hp SeaHorse from 1979.


Please see the video below i took today:



The idle screw as you can see does not return to its stop. I've linked and synced as best I can with this old thing, but this last bit is beating me.

When i push it manually it idles fine and everything else looks to be working as it should be, at WOT the butterflies are straight open, its just when I return back to idle/neutral the throttle cable doesn't seem to push it far enough back.

As I see it adjustment wise I can

1) Adjust the trunnion adjustment nut but as you can see i've done this and its already maxed out (this in itself is a bit suspicious?) so wont go any further.

2) Adjust the "throttle cam yolk" but I'm not convinced that this will really push the idle part back enough and by adjusting this I get all the cam markers etc messed up (which causes me other problems at WOT etc).

I recently took off the entire throttle arm, spring, washers etc and cleaned it all out and re-lubricated using gear oil hoping that would fix but it didn't help.

I'm suspecting the throttle cable is stretched and worn? Its the original one I think probably never changed (from 1979!) so this would seem a likely culprit.

Any other ideas or anyone experienced who can confirm my thinking?

I'm pretty sure the throttle cables have never been swapped out (they are OMC ones and think theyre original).


I'm considering opening up the remote control box - I got a tip that you can adjust the length of the cable there (its already screwed in the maximum as you see in the video via the trunnion adjustment plastic screw).


Failing that I have a feeling a new cable might fix it I guess it makes sense to get both cables.


Any ideas how I go about knowing how long my cable it bar taking it out and measuring it? And If thats necessary, do you know where I measure from and to in order to get the right length measurement?

You can have a look , by all means.------But these cables are not meant to be adjustable.----Earlier control boxes they were !!

may need to clean and lube under flywheel