shift linkage 1964 Merc 3.9

[freddyray21]

picked this one up at a sale the other day and got it running yesterday. It will need an impeller and I have one ordered locally will be here tomorrow. No problem with the impeller change though. For the short time I had it running it seemed to want to go from neutral into gear by itself. It I held the gear shift it would not, but leaving it alone it would shift. I have another one of these motors also very similar a 1972 4hp and the shift lever is set in a different position. To explain, looking at the gear shift on the 72 from the side neutral is in about a 12 to 1 o'clock position. On the 64 neutral is in about the 3 o'clock position. When I dropped the lower unit to replace the impeller there was no shift linkage to unhook. Just the shift shaft lined up with grooves to it's mate. Is is possible some PO put the shift lever in the wrong position when they put it back together and that is why it wants to shift on it's own. I need to get this fixed as it needs to have a reliable neutral to be a usable motor.

 

[Laddies]

Re: shift linkage 1964 Merc 3.9

The detent on the shift cam is worn out probably need to replace it and the shift follower pin

 

[AMD Rules]

Re: shift linkage 1964 Merc 3.9

I agree, sounds like your detent on the cam is not holding it in gear. You will also find on the powerhead, there is a piece of spring metal holding the horizontal shift arm in position. There is a cam on that arm as well. Check that out.

Attached a pic of the lower unit internals, so you can see the shft cam. Pin is spring loaded riding against the cam, and goes into the end of the left side of the prop shaft.

 

[freddyray21]

Re: shift linkage 1964 Merc 3.9

Got it back together. Turns out whoever had it apart the last time did not have the shift lever in the right spot where it would hold in place. I put the shift lever and the lower unit both in reverse and put it together. Will idle all day now and stay in neutral. You were right on track.

 

[freddyray21]

Re: shift linkage 1964 Merc 3.9

it was the cam on the powerhead.

 

[freddyray21]

Re: shift linkage 1964 Merc 3.9

I agree, sounds like your detent on the cam is not holding it in gear. You will also find on the powerhead, there is a piece of spring metal holding the horizontal shift arm in position. There is a cam on that arm as well. Check that out.

Attached a pic of the lower unit internals, so you can see the shft cam. Pin is spring loaded riding against the cam, and goes into the end of the left side of the prop shaft.

holding in gear was not the problem. keeping it in neutral was. It wasn't jumping out of gear it was jumping out of neutral due to as I suspected the cam on the shift arm not being in the right place, but your posts cause me to look at that. The two motor while seemingly the same have a different cam device in the shift arm.