1975 Mercury 50HP (500) Shifting problems - barely engaging reverse

[Sidhewynder]

Hi. Years ago I purchased an older boat that had been sitting for some time with a Mercury 50HP (500) outboard. Serial # 4286099. If my searches are correct, that makes it a 1975 model. The boat sat in my backyard for a long time awaiting free time; recently I got that time. When I purchased the boat, the motor would go into drive (prop ratchets in one direction, locks in the other), but I had to pull the shift lever back past the neutral detaunt into the reverse area to get neutral (prop spins freely both directions) and pulling the control lever clear back would barely pull the drive into reverse (prop spins in both directions with a clicking sound each way). I thought that the cables just needed adjusted and given the price of the boat/motor and the fact I wanted to learn about outboards, I drug the boat home.

Yesterday I removed the lower unit to replace the water pump impeller. I put the drive in forward and pulled the lower unit. When the lower unit came out, several pieces fell out. The water tube, exhaust tube and two plastic pieces from the front dropped on the ground. I have an older style lower end with a pre-load pin on the drive shaft. After replacing the impeller and much gnashing and grinding of teeth, I got the lower unit re-installed ? only to discover the motor was locked in forward. Long story short ? after uninstalling and installing the lower unit (and putting those two plastic pieces that fell out in the front in various configurations), I?m left with a motor that has forward, neutral past the detaunt in the control box and reverse that ratchets in both directions. Exactly where I started- just with a new water pump impeller.

The lower unit is the older style with a square shaft assembly whic slides into a square tube in the motor leg that rotates and selects the gears. Through trial and error, I discovered that shaft in the lower unit can rotate in either direction before engaging the gears (which gives the added bonus of being able to install it exactly backwards ? ask how I learned that little fact). After getting nowhere I took the lower unit back off and using a wrench to move the square shaft I can get a solid forward, completely free neutral and solid reverse (locked in both directions). With the motor in forward, I reinstalled the lower unit and disconnected the control cables, I worked the gear selector mechanism with a screw-driver where the cable connects. Looking at the slide where the control cable connects, if the slide is all the way front, I have a solid forward. As you push the slide towards the back of the motor it slips into neutral (about half to 2/3 of the way back the slide rail). When I move the slide clear to the back of the rail and keep a constant pressure on the slide traveler, I get a ?better? reverse (more ratcheting/catching) but still not solid like when the lower unit is off. There isn?t any adjust on the arm that connects the slide to a bellcrank (which is connected to that square tube that runs down the motor leg to the gear selecting rod in the lower unit).

So.. help! Does the prop on these motors really not lock solid both ways in reverse? Do I have the ?best? reverse I?m going to get? If they do lock both ways in reverse, how do I adjust I adjust things to get a more solid reverse? Have I just managed to move that gear selecting shaft into the wrong position? There?s a lot of play in that shaft. I think I have that plastic reverse locking cone in the correct position because the whole motor will pivot up when the selector is in forward, but locks when put in reverse (well, what little reverse I seem to have).

While you?re reading this, what is the proper or best way to adjust the control cables?

Apologies for the long post, I just don?t know the technical terms of the components, so I had to describe what they did.

THANKS in advance!!

 

[oldman570]

Re: 1975 Mercury 50HP (500) Shifting problems - barely engaging reverse

The prop should ratchet one way when in forward and lock complety when in reverse. The plastic reverse ramp on the LU shaft is in correctly as the motor locks down in reverse. Try taking the shift link from the control off its pin where it goes in the motor and place the motor in the most centered nutral position and adjusting the control link to fit the pin after hook it back to the shift lever first. It should lock the prop in reverse when shifted to reverse and forward when shifted to forward but ratchet when the prop is turned the worng way. Most all Mecr controals cables will work on the motor unless the cable has been replaced with something other than the correct one. Only other trouble that can cause ratching is a worn reverse gear or cluch dog in the LU. JMO!
Oldman570

 

[Sidhewynder]

Re: 1975 Mercury 50HP (500) Shifting problems - barely engaging reverse

Hi Olds,

Thanks for confirming the reverse ramp is in the correct position. With the control cables completely off the motor it still won't lock in reverse. I can push the control slide (where the cable would hook) clear to the back of the slide rail and it won't lock in reverse. If I take the LU off and work the gear selector shaft with a wrench, I can get reverse to lock. So I'm thinking its either like you said the gear or dog being worn so much that you have to turn the selector shaft farther than normal to get the gears to lock in or the selector shaft is so worn somewhere it has to turn farther than normal to engage reverse. I figure you'd have to tear down the LU to check the gears, but is there a simple way to remove that selector shaft without a full tear down. Pictures in the manuals for the shaft aren't real clear, and the instructions for removal are always part of a complete tear down.

Thanks also for how to correctly connect the cables (when I get the reverse thing figured out, or decide to live with what will probably be very slow reverse.. or none at all).


Thanks

 

[oldman570]

Re: 1975 Mercury 50HP (500) Shifting problems - barely engaging reverse

Special tools are needed inorder to tear down the LU of that motor. A spanner wrench for the first nut holding everything in the gear case and gear lash gages for the proper gear clearance if rebulding the LU compleatly. Parts can be bought fairly easy but check the $$$$ before hand as it could change things. Good rebuilt or used LU's can be bought also, sometimes for a good price.
Oldman570