Merc 20-Weird shift shaft problem

crammit442

Recruit
Joined
Aug 3, 2011
Messages
2
I'm new here and have searched, but can't find exactly the same problem I'm having. I've got a '79 or '80 (ser #5086064) merc 20. It ran well last time it was run 5 or 6 years ago. I just finished new jon boat and rebuilt carb on motor to be safe. Got to the lake and the motor ran great the pisser wasn't pissing. At first I figured just dirt dobbers as always, but after cleaning pisser and tube, it turned out to be be the impeller. Should've known after sitting that long.:facepalm: I ran into town and got a replacement impeller and had it installed in no time. I've changed it before on this motor with no issues years ago, but this time when I launched the boat I had three fwd gears. I've disassembled the LU probably 50 times and reinstalled with the shift shaft/shift lever in every possible combination and no matter what I do I come up with multiple fwd gears. The best luck I've had yet was a neutral and two fwd's. I successfully got it installed with both shaft and lever in neutral tonight and all was well until I cranked the motor and it only stayed in neutral a second or two before returning to fwd in all three shift positions. Any ideas? I suspect I'm missing something really simple, but the manual is pretty vague(clymer) and I'm just not that familiar with outboards. I've built and run many race jetskis(standups), but their drivelines are much simpler. Thanks in advance!:)

Charles
 
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crammit442

Recruit
Joined
Aug 3, 2011
Messages
2
Re: Merc 20-Weird shift shaft problem

TTT. Anyone? I'm stumped and there isn't a shop near here that isn't backed up for weeks or months. Thanks!
 

gjeka02

Cadet
Joined
Jul 23, 2011
Messages
18
Re: Merc 20-Weird shift shaft problem

I installed a new water pump on my 1982 Mariner 50 which has a reverse cam. I uses a E12 reverse torx socket and it fit perfect on my 3/8" outer diameter spline shaft. I simultaneously moved the prop CCW and the spline shaft moved easily. I set the spline to neutral with the prop spinning freely in both directions, the top of the ramp on the reverse cam is lined up perfect with the front of the motor. Make sure your shift knob is set to neutral when you reinstall the lower unit. When you get the unit up lightly tighten the two side screws partially. Check that the shift knob shifts through the gears.
 
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