Mercruiser Pre-Alpha (EZ Shift or MC1) shifting issue

[Tix]

Hello,
I have an old GM inline 6 160hp engine and a prealpha mercruiser outdrive (it's either an EZ shift or a MC-1, I forget exactly). But it's having a shifting issue that I can't quite pin down.

My shifting setup is pretty standard—I have a single lever throttle/shifter up front, and just two gears and a neutral. It used to work great, neutral was right in the middle, and forward on the lever was forward and backwards was reverse...the lever would go about 3/4 of the way forward and about 3/4 of the way backwards. The last few times I've run the boat have just been dockside, so I have no idea when this issue started, but now the shift controls seem all messed up. Long story short, it doesn't seem to catch in forward gear. I can throw the lever all the way forward and forward gear doesn't engage, and I can only pull the lever about 1/4 of the way backward.

I pulled the lower unit off, and I can get the gears to engage properly in the lower unit just by manipulating the shifter by hand, so the problem is somewhere in between the throttle and the upper unit. I actually think it's not the cables, because if I disconnect the cables at the motor/transom, the cables shift fine (all the way forward and all the way back).

I'm not sure what to check next. I think the issue is somewhere in between where the cable dead ends at the transom and the lower unit, which makes me think that something is going haywire in the upper unit... but I have no idea wha to check or what to look for or really what happens inside the upper unit at all.

Any guidance would be appreciated, thanks!!

 

[Scott06]

I think with the drive put back on the boat you should be able to disconnect the lower shift cable in the engine compartment and shift it by hand should easily slide in and out of gear with two fingers.
while you have the drive off try it if ok reinstall the drive and try again. This will isolate from helm to engine compartment, engine compartment to drive

 

[1960 Starflite]

One of the shift cables has slipped. As stated above, remove lower unit shift cable at engine bracket to see if you can shift into forward and reverse there.

While lower unit is off is a good time to replace water pump impeller.

 

[Tix]

Hi, yes, I think the issue is that even with the lower unit off the and shift cable disconnected in the engine compartment, it don't shift. My understanding from the manual is that when I shift by hand in the engine compartment the little cylinder spline in the upper unit should rotate. It rotates when I try to shift into reverse gear by hand and rotates back to neutral but it doesn't rotate into forward gear.
Or maybe I am fundamentally misunderstanding something about the way things are supposed to work?