Merc 850 Shifting Woes

[Todd Gerber]

I know there's been several threads regarding shifting issues, but I didn't find much help with those.

Here's my issue: Bought a used 1974 850 that runs good. Previous owner stated the owner before him had $600 into the lower end (doesn't know exactly what was done.)

When it out around the lake and it ran great. Only issue was it seemed to grind all the time in reverse - but it worked. Forward was fine.

Dropped the lower unit to change the water pump. Got it all back together, didn't touch the shift shaft, unit wouldn't slide back together. Started messing with the shift shaft and it seemed the reverse lock-out cam was not in the correct spot. Repositioned that, messed with the remote control and turning the shift shaft and got it close - only 1/2 gap now. Fight with that later.

My biggest issues is with the gears. I can either get full foward, neutral, and partial reverse, or full reverse and partial forward. Looked into adjusting the shift cable, but that didn't seem to help. I can't seem to keep it in one or the other.

It almost seems the lower unit shift shaft needs to rotate farther than the socket in the power head unit. Can that be true? It looks like the power head socket is only rotating a 1/4 turn to forward and reverse from neutral. Does that sound right?

I can set the reverse cam to the correct position, but then it doesn't seem to want to go into forward.

I've a few hours on this now and haven't really gotton anywhere. Unless anyone has anything to try, my next step is to take the lower unit to the shop and have them make sure everything is correct there. I'm not convinced that it is.

Thanks for any comments,

 

[Chris1956]

Re: Merc 850 Shifting Woes

Todd. It kinda looks like the shift cam is broken and the angle is too steep. This will make for hard shifting.

First put the lower and MerControl into neutral. The LU will stay in neutral, aming installation easier. Make sure the plastic upper shift rod guide is installed in the midsection, around the shift rod. Now the reverse lock should be engauged when the motor is in reverse and neutral, and disengaged when in forward. I suggest you adjust it so it does not engauge at all, until you get your gears working. Now install the LU. Grease both driveshaft and shift shaft splines. Remove the spark plugs and turn the flywheel as you install teh LU. When the driveshaft lines up, the halves will just about mate. make sure the shift shaft doesn't pop up under the carbs. You may need to rock the shifter a bit to mate 'em.

One more thing. There are two neutrals in the LU. The neutral you want is where the reverse lock cam is engaging the reverse lock rod. If the reverse lock cam is bad, replace it, or disengage the feature.