1963 Merc 850 spins freely in reverse

[hoffmanuno]

I have a 1963 Merc 850 I restored. I took off the lower unit to torch off the prop hub (it had sat unused for over a decade), and had a shop install new prop seals. Before this, it shifted into rev, neu, and forward fine. After getting it back and putting a new impeller and driveshaft sleeve and seal on, it now spins freely in reverse. I took an old shift rod off a merc 650 to align the cams, and it worked fine. With lower unit off cam clicks from forward, to neutral, and they work fine, but when you turn the shift shaft into reverse the prop spins like it did in neutral. This is all the same when it is bolted to the outboard and using the shifter on the boat. I havent tried shifting it with the motor running yet. Reverse just doesnt seem to engage anymore no matter where you turn the shift cams when off the outbord using the spare shift rod. Could heating the prop, and we had to heat it up to remove both the prop and hub, have caused the reverse gear to stick inside? There were no metal shavings in gear case before or after and it shifted fine before removal and heating? Im thinking reverse is stuck and may shake loose if I run it. Any ideas?

 

[Texasmark]

Re: 1963 Merc 850 spins freely in reverse

The forward and reverse gears sit on the prop shaft and are in constant engagement with the drive shaft. That means if the engine is running, they both are turning; one cw, the other ccw.

Shifting is accomplished by a shuttle gear called a clutch dog that is made to slide back and forth along the propshaft by the shifting fork. Whichever gear it is pushed against determines your direction; if sitting in the middle and not touching a gear you are in N. Clicking in F is how it works if cw rotation, and engagement in ccw direction.

R is a straight sided cog type gear and you have to have them lined up to get it to go into R. Either the engine has to be idling or you have to slowly rotate the propshaft while putting pressure on the shifting shaft spline.

The first thought is that your shifting fork is not pushing the dog far enough backwards. If someone has forced it into R they could have bent the shifter and caused this problem.

Nothing there that is heat sensitive; only seals that hold your oil in.

I'm assuming the reverse gear (the actual gear) wasn't removed for some reason and not reinstalled.

HTH,

Mark

 

[hoffmanuno]

Re: 1963 Merc 850 spins freely in reverse

I started up my outboard today and went thru the shifter and by hand to shift the outboard. Forward engages fine, neutral engages fine, but reverse is still not engageing with the outboard running. In reverse, the prop does not move, just as in neutral. The shift shaft seems fine. Reverse is not supposed to engage with the engine not rotating, but it shifts smoothly at the shifter in reverse but yet does not engage. The reverse transom locks work perfectly, but does not engage. I notice that with the shift cams out I can turn the shift shaft clockwise or counter clockwise to engage forwardl, neutral, or reverse. I do have the shift cams aligned properly (Im pretty sure) because I set it in forward to match the rotation of my outboards shift rod's turning (counterclockwise). Im at a loss. It shifted fine before I took it off and replaced the seals and cleaned it up (which is when I took out the cams to inspect the seal. Should the shift rod in the lower unit rotate in any direction? Im hoping there is an easy fix. I would really like to have reverse before I take it out on the water.

 

[hoffmanuno]

Re: 1963 Merc 850 spins freely in reverse

Just wanted to add/emphasise that the shift shaft in the lower unit turn freely in both directions, stops and clicks for forward, neutral, and reverse (though reverse does not engage). Is this shaft supposed to spin in both direction without hitting a permanent stop of some kind? Im wondering if something is now broke off inside, but I never forced it, just turned it with an old shifter rod from a scavenged housing.