89 Mercury outboard 100 hp shift shaft alignment

[dmiles452]

I replaced the water pump in the lower unit and now I have nothing at the prop. I tried the method listed on another page of turning the lower shaft all the way CCW until it clicks and this should have been neutral. But I still have no drive at the prop.I have changed several water pumps and never had this problem. Any advice would be appreciated.

 

[Texasmark]

If you only changed the water pump your lower unit should still function. The shifter splined shaft (stub) sticking out the top of the LU is embedded in a piece of metal (bar) at the front of the LU, internally. On the other end of that bar are 3 detents, each being a different dimension from the location of the splined shaft insert.

Sticking out the front of the prop shaft is a pointed "cam follower" that rides along the 3 detents. The position of the cam follower determines the location of the "clutch dog" that is installed on the prop shaft. The dog has teeth at both ends, a sawtooth on the front end and a set of square stubs on the other.

The sawtooth fits against the F gear when the cam is in the closest position to the splined shaft. N is the middle slot having no contact with either gear, and farthest away is the R slot.

I like to use N, the center slot as I can move the splined shaft back and forth and feel both F and R detents. I then set the remote control to the N position.

The unit is installed in the midsection and goes all the way up and meets the midsection or it stops about 1" from that contacting surface. With the latter, the splines of the crankshaft and the drive shaft aren't lined up and they need to be lined up for it to close the 1" gap. You can't move the driveshaft with the prop because the LU is in N so you have to turn the crankshaft. I use a socket and wrench on the flywheel nut to accomplish this task. You keep light pressure on the LU as you slowly turn the wrench and when the splines line up the gap will close.

Some people use F or R gear since in either of those gears you can turn the drive shaft by rotating the prop which is more convenient for them. I use N because in positioning the clutch dog initially I know that I am in N and not F or R since I have them on either side of the N position.

A lubriplate or other water resisting grease should be applied lightly to the splines prior to assembly but no grease on the tip of the shaft as it may impede the mate up because it would get wedged between the tip of the drive shaft and the matching hole in the bottom of the crankshaft.

 

[racerone]

Make 100% sure that gearcase in in neutral.------Have control in neutral.----As you assemble make sure that gearcase is still in neutral.-----The spring loaded clutch dog can jump into forward.

 

[BWR1953]

Hey guys, I'm having the same problem getting my LU back into place on my 1983 70HP Merc 3 cylinder. (BTW - I have physical limitations and can't do this job by myself.)

There was no remote control connected to the engine when the LU was removed. The indicator on the engine shows that it is in neutral.


The lower unit is in neutral as well. I can spin the prop shaft easily by hand in either direction.

I've read this thread and just can't seem to get things lined up. My 17 y.o. stepson is helping by pushing up on the LU while I steady the engine and slowly rotate the flywheel in an effort to get the crankshaft and driveshaft aligned. Still no joy.

I watched this video and learned how to shift the LU from F-N-R but didn't get anywhere with that.

As of now, the engine is just on the stand with a ratchet strap to hold the LU in place. Any other tips or tricks to get the thing lined up?

 

[Chris1956]

The driveshaft will align first. That should be easy if someone turns the flywheel. Remember to grease the splines. If you can tilt the motor up, it makes the gearcase lighter.

The shift shaft is another matter. I often need to grab the shift shaft with a needlenose plier and move it into place to mate with the gearcase shift shaft. You also may need to wiggle the shift slider to line it up better. Remember the shift shaft has 8 (or so) splines, So the shift shaft could need to turn 360/8 degrees. usually it is much less.

 

[merc850]

If you can tilt the motor up, it makes the gearcase lighter - try to get it as horizontal as possible, since you don't have the manual reverse lock installed you will need to grab the shift shaft with a needlenose plier and move it into place Some driveshafts have a pre-load pin that gives some resistance to engagement. I usually do the front nut first then turn it slowly while checking the mating.

 

[BWR1953]

Fixed!

My neighbor buddy came over and manhandled that thing with channel locks and brute strength and got the LU installed! Everything is installed to correct torque and no parts left over.

All I had to do was provide torque specs and entertain his 6 y.o. son.

 

[merc850]

Fixed!

My neighbor buddy came over and manhandled that thing with channel locks and brute strength and got the LU installed! Everything is installed to correct torque and no parts left over.

All I had to do was provide torque specs and entertain his 6 y.o. son.

Does it shift correctly? Turn the prop while shifting into reverse.

 

[BWR1953]

Does it shift correctly? Turn the prop while shifting into reverse.

Yes, it does. He was constantly testing as he worked. He whaled on that thing like it owed him money!

 

[BWR1953]

FYI - my engine isn't running yet. I have to install the airbox and whatnot before I can test it with it running.

 

[Chris1956]

Gee, the fit of the gearcase to the midsection is tight, but usually wiggling it with hands is enough to slide it in. I would watch for stripped driveshaft splines and cracks in the midsections.

 

[BWR1953]

 

[BWR1953]

...you will need to grab the shift shaft with a needlenose plier and move it into place Some driveshafts have a pre-load pin that gives some resistance to engagement. I usually do the front nut first then turn it slowly while checking the mating.

This is exactly what my neighbor buddy did. It worked perfectly.
Thanks!

 

[Chris1956]

Gee, "Whaled on it like it owed him money" seems like overkill to me. I wiggle the gearcase, tightening the nuts with my fingers until she is just about all the way mated with the midsection. Then I use a wrench/socket to tighten.