Reverse Locking Cam

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: Reverse Locking Cam

OK, you'll notice that the upper reverse lock cam has 2 'ears'. These go side-to-side always, as they have to slide upwards into the exhaust tower to operate the reverse lockout rod.

Now, when the lower unit is in Fwd, the upper and lower cams 'nestle' into each other. Such that when the shift shaft is rotated CCW to shift first to Neutral then to Reverse, the upper shift cam 'walks' up the ramps of the lower shift cam as the lower cam turns with the shift shaft.

I'm assuming you've removed the lower cam from the shift shaft and lost its orientation. So we need to fix that first.

You'll need to make sure the lower unit is shifted to Fwd gear. If you turn the driveshaft CW as you're looking down at it, the propshaft should also be turning clockwise.

Slide the lower cam on the shift shaft, any old way and rotate the shift shaft as required to get to Neutral. Verify the propshaft turns freely in both directions.

Then, rotate the shift shaft clockwise until it clicks into Fwd then STOP! Don't move it from this position.

Note the position in which the lower shift lock cam must be, in order to 'nestle' with the upper cam. And realizing that the ears on the upper cam have to be side-to-side.

Or, just slap the upper cam on the lower cam, let them 'nestle' and install like that on the shift shaft, with the upper cam's ears side-to-side.

What you'll also notice is that a line drawn straight across the 2 'ramps' on the lower shift cam will now align with one of the gearcase mounting studs.

Make sure your lower unit is still in Fwd gear. Also make sure the shift lever on the motor is in Fwd.

You should now be able to install the lower unit with all your shifting functions intact.

HTH & Have Fun!.............ed
 

Dreworr123

Seaman Apprentice
Joined
Jun 15, 2010
Messages
41
Re: Reverse Locking Cam

Thanks Ed for the great reply! I did what you said and when I shift back into neutral it will stay in forward. Then when i shift back into forward it goes into neutral. What could I be doing wrong?
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: Reverse Locking Cam

OK, maybe that one shifts in the opposite direction! So you're saying that you rotate the shift shaft Clockwise to get from Fwd gear to Neutral?

Most (not all but the majority) of big Mercs shift Counter-Clockwise to get from Fwd to Neutral to Reverse. Any more rotation in the CCW direction (if possible), would cause the L/U to drop back into Fwd gear. Then, if you continue rotating the shift shaft in the CCW direction, you'd eventually get to the point where it'll shift into Neutral, then Reverse.

Anyway, what you need to do is figure out where Neutral is then shift right back to Fwd, only turning the shift shaft as much as it takes to get into Fwd and no more.

It's at this point the reverse lock cams can be assembled with the 2 cams 'nested' into each other.

I guess it's immaterial which way the shift shaft is rotating, just so long as you're at the point in Fwd gear where any more motion will shift to Neutral. It's possible to move the shift shaft around a whole bunch more when the gearbox is in Fwd, but if it's off you'll only get Fwd gear (that's what usually happens).

So, anyway, get 'er clocked correctly and I bet she goes back together nicely.

HTH.........ed

p.s. I didn't ask but is it all back together and you're shifting from the control box? Here's a hint, the shift lever on the side of the motor goes all the way back for Fwd gear and all the way to the front of the cowling for Reverse, with Neutral of course being somewhere in between. Maybe that little clue will help you figure it out.
 
Top