Mercury Model 850 reverse lock cam alignment

NatefromOgden · #1 September 18th, 2009, 12:04 AM

My motor's a 4 cylinder, I think its a 78 model, (sn 4540754). After having the lower unit resealed I discovered the motor would no longer lock to the transom when put into reverse. I removed the lower unit and discovered the reverse lock rod cam was broken, (plastic) so I bought a new one that is metal. I cannot get the cam alignment set properly. I also replaced the rod guide with a new one.

Set on the splines where the mechanic put it, the motor doesn't unlock until the shifter is placed into drive and it relocks before getting into neutral. When I rotate the cam 1 spline backwards to move the ramp away from the rod, the motor won't lock down in any shifter position.

It shifts into forward and reverse easily so I think the shift cables and adjustments are correct but I cannot figure out this reverse lock problem. I've had the lower unit up and down most of a dozen times and I can't get it right. Please advise.

emckelvy · #2 September 18th, 2009, 02:02 AM

Your reverse lock is working normally. It is supposed to lock in both Reverse and Neutral.

So, to tilt the motor up just leave the control box in Fwd and don't shift out of Fwd until you place the motor back down on the tilt pin. If you shift out of Fwd with the motor tilted up and then lower the motor, the reverse lockout hooks will bind on the tilt adjustment pin and cause balky shifting action.

The correct position for the cam is, when the lower unit is shifted to Fwd and just about to shift into Neutral, the reverse lockout rod points to a position on the shift cam ramp approx halfway up the ramp. Such that as soon as the shift shaft is rotated CCW to Neutral, the flat part at the top of the shift cam blocks the spring-loaded lockout rod from dropping down, effectively "locking" the hooks into place.

HTH.........ed

NatefromOgden · #3 September 18th, 2009, 11:14 AM

I'll drop the LU again today and go with your expertise and recommendation. Before I had the lower unit off for an impellor change and reseal, it was unlocked in neutral and locking in reverse but perhaps that was a result of the failing cam.