'74 Merc 500 shift shaft question

[TriadSteeler]

I have a 74 Merc 500 (SN #8323131) that I am in the process of reviving after a 10 year hiatus.

I dropped the lower unit (in forward) in order to replace the water pump. The prop shaft would engage the drive shaft in the proper direction and click in the other. After I removed the top cover from the water pump, spinning the prop shaft in either direction spins the drive shaft in either direction. In addition, the shift shaft turns a 1/2 turn very easily (without engaging anything) in either direction and then will stop with some resistance (kinda springy).

My question is: should there be any play in the shift shaft or is it plausible that the shift shaft either sheared off or came out of the shift cam and should you be able to shift via turning the shift shaft relatively easy (with your fingers). I didn't want to force it, and I don't want to put it all back together if I need to tear into the shift shaft.

 

[tmcalavy]

Re: '74 Merc 500 shift shaft question

Had a 73 Merc 500. Always had to use a pliers gently to get the shift shaft to engage/disengage with the LU off. Once took the LU to my marine shop and a kid there somehow slipped the shaft off the cam. The older mech made him drop everything else and get it back together. In short, if you can spin the shift shaft by hand with little or no resistance, it's probably come off the cam. Only way to be sure is put the LU back on. If it shifts normally, your okay, if not...time to go inside and check the shaft and cam connection.

 

[Scaaty]

Re: '74 Merc 500 shift shaft question

I think your fine on this statement...just pulled a 62 apart, and there is a lot of slop there....same way
a 1/2 turn very easily (without engaging anything) in either direction and then will stop with some resistance (kinda springy).

No way in hell on this statement...your pushing on a spring in there without the advantage of leverage from the shifting mechanism from the lever all the way down to that spring in the mainshaft..
you be able to shift via turning the shift shaft relatively easy (with your fingers).

 

[TriadSteeler]

Re: '74 Merc 500 shift shaft question

Thanks folks, I appreciate the advice. The manual just made it sound like a breeze to shift between F-N-R by turning the shaft.

 

[Scaaty]

Re: '74 Merc 500 shift shaft question

Don't mess with it. Just wrap it up...if a problem THEN, we can work it out

 

[TriadSteeler]

Re: '74 Merc 500 shift shaft question

Turned it with the pliers. Went right into neutral then in reverse. Verified it by the actions of the prop shaft. BTW, when in forward and the water pump is off, the drive shaft and prop shaft will spin in both directions. If you hold the drive shaft still, the prop shaft will ratchet like normal. It was the pressure of the impeller holding the drive shaft still. (Scaaty may be crazy, but nailed this one dead on.)

For Future Folks searching the forums with this same issue:

[Looking at the Lower Unit from the stbd side] When the LU is in forward the shift shaft will freely turn clockwise until the top of the ramp on the reverse cam reaches 12:00 it will also turn "freely" counter clockwise until the bottom of the reverse cam reaches 3:00. At this point you will feel resistance. In neutral the middle of the ramp will be at 3:00 and when in reverse, the top of the cam ramp will be at 3:00 (right beneath the pushrod for the reverse lock).

This may also help folks who are replacing the reverse cam and didn't mark the alignment when it was removed.