Reverse Lock Cam and related parts to shift

[ddiggerr]

Good day all,

I have dropped lower unit to find out why I have no reverse. There are 3 parts that have me confused as to how they are to be correctly installed. The previous owner changed impeller and advised me there was no reverse since he did the job.

This is a 75 Mercury 500 50hp. I have attached pics of the parts in question as I cannot find any info as to how they are to be correctly put back into place.

Any help would be greatly appreciated.


The peice on the left looks like a chunk is missing.

 

[turtles11756]

Re: Reverse Lock Cam and related parts to shift

reverse lock cams .the one on the left fits on the lower shift shaft.go to crowley marine site and check the parts catalog for your model. if not correct the lower will not come back together right .you need a manual

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift

Thanks for the info. I have a shop manual which does not show placement of these parts. It does mention them breifly, but thats it. I put back together, but still not correct as it does not engage reverse.

Trying to figure out which direction they go, IE: tapered side up or down, facing back or front.

 

[egclassic]

Re: Reverse Lock Cam and related parts to shift

The part on the right goes into the motor housing (not the lower unit), you should also have a coupler because that is what lines up the upper shift shaft to the lower shift shaft.
The part in the middle goes over the lower shift shaft, grooved side down, there should be slots in the lower unit around the shift shaft.
The part on the left goes on top of the part in the middle and it does look worn. You will know if it is installed wrong, if you try to tilt the motor up when it is in forward gear and it won't budge. I believe the "high" side should be facing the right of the lower unit housing, if you have the gear case in forward. This part pushes up on the locking mechanism when the controls are in reverse to keep the motor from lifting.

 

[Jacket4life]

Re: Reverse Lock Cam and related parts to shift

None of those parts will fix your problem of no reverse. THey are for a different function (i.e., they keep your motor from "kicking up" when it IS in reverse)

Read this thread and see if it doesn't help:

http://forums.iboats.com/showthread.php?t=388816

The problem is the P.O. messed with the lower shift shaft while he had the lower unit out to replace the impeller (he probably didn't do it on purpose, or didn't realize it was going to be a problem) you have re align your gearing where it is supposed to be when you re-install it.

Hope this helps!

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift

I believe the "high" side should be facing the right of the lower unit housing, if you have the gear case in forward. This part pushes up on the locking mechanism when the controls are in reverse to keep the motor from lifting.

Should there be something other than the shift shaft located in this area? When all is put back together, there is nothing this peice would push against to lock.

Even looking up into upper half is just the shift shaft coming down to meet the lower unit shift shaft.

 

[Jacket4life]

Re: Reverse Lock Cam and related parts to shift

My motor has trim and tilt, so I'm only passably knowledgable about how the reverse lock works, all I'm saying is that the parts you have listed and the problem you have aren't related. Not saying you don't need to fix both, just that fixing your reverse lock won't fix why your motor won't go into reverse.

 

[egclassic]

Re: Reverse Lock Cam and related parts to shift

I agree with the rest that these have nothing to do with it not going into reverse. But if not installed correctly, your motor will not "lock" down when in reverse. You should see the rod up in the housing that the reverse cam "pushes" against. It is next to the shift shaft, at least on my 850 it is.

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift

Thanks for all the suggestions. I have power trim/tilt and do not see any other rod coming down by the shift shaft. I have also dropped lower unit and verified it shifts nice and easy in F-N-R off the motor.

I have adjusted cable, thinking this was the problem, however, no matter how much I adjust it, it always seems to not push it into reverse when all put back together. I have verified there is no abstructions of any kind preventing the shift shaft not to turn as it turns freely with lower unit off when shifting.

Even shifting manually, with shift cable removed, will not allow me to push shift arm into reverse. Its like there is something stopping full movement. It looks like I only need about another 1/4" for full reverse. But cannot see what would stop full motion.

Also when I shift from F-N, the prop now makes a slight ratcheting. If I go from R-N, then it stops. I am confused and ready to throw in the towel, but can't bring myself to pay someone $500-$1000 to fix, because I know this has got to be a simple fix. I just can't see it.

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift

One more question. Are the pieces I have mentioned earlier, and have included pics of. Are these needed with power t&t?

Could they actually be removed all together and the shift still function?

 

[Jacket4life]

Re: Reverse Lock Cam and related parts to shift

All I can tell you is that they ARE NOT in my '73 Merc 500 and my motor works fine without them. IDK if they SHOULD be removed, or MUST be removed, or what. All I know is that they are not in my motor. Hope that helps?!?!

 

[chum1]

Re: Reverse Lock Cam and related parts to shift

Hello Dig, I just went through the lower end on my 77' 850( not that it makes me an expert but i may be able to give you some pointers)

1) the two left plastic pieces are for the locking mechanism on engines not equipped with power trim/tilt, there good to have in in case the engine ever goes back to a tiltless/trimless motor, The one piece on the far right is needed so the shift shaft lines up on installation of lower end.

2)before installation of lower end make sure shift shaft is in the neutral position, then make sure your throttle handle is in neutral position. Verify the shift cable end is in about the middle position (neutral) and will drop into pin, if not adjust cable. Install lower end.

3)If going from forward to neutral makes a slight ratcheting noise it may indicate a cable linkage adjustment problem

4)you should be grinding gears so to speak as soon as the throttle leaves the neutral detent in both fwd and reverse

 

[Wingedwheel]

Re: Reverse Lock Cam and related parts to shift

OK I had pretty much the same problem and after replacing the shift-cam, cam follower and pretty much tearing my hair out, I figured out the problem was between the shift block and the lower unit. That left only the shift-shaft coupler. After dropping the lower unit, I looked up at the coupler with a flashlight and sure enough, the splines were pretty worn. Forward gear is spring assisted and reverse is spring opposed. There was not enough "meat" on the splines to get the cam past the spring tension. Works like a charm now.

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift

Once again, thanks for the suggestions. I have checked and double checked everything.

LU shifts perfectly into F-N-R when removed. When all back together, will not budge when attempting reverse.

Cannot adjust shift cable any further as it is at end. With cable disconnected, still cannot shift into reverse manually.

Upper shift rod is moving in the direction of reverse when LU is removed, however does not appear rotate far enough.

My question now is, can the upper shift rod be adjusted, as it appears to me as though it is off just enough to not fully engage and the shift cable is adjusted to its max and barely reached N when coming out of F gear. I have to go past N into R position to get into N.

I ask about the shift rod adjustment due to me not finding any info online or in manual.

Thank You

 

[MatchT]

Re: Reverse Lock Cam and related parts to shift

Hello, my engine is also doing the same...I cant get it to go in reverse in the water...

My theory on mine is that the upper shift rod, rides up too much and is blocked by the lower carb housing....

I am curious to see if the coupler could be worn out as well.

with my LU not installed I can rotate the upper shift rod all the way back and forth on the travel length of the shift cable,

good luck and post results as well....

Match

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift

Well after doing alot of reading tonight and having a look once again at my shift assembly, it appears all my troubles are pointing towards a twisted upper shift shaft.

This would explain why I cannot fully engage reverse and why I need to go just past N to get to N.

It looks slightly twisted, but not much. I am hoping I can realign this without needing to remove powerhead. Will update with results

 

[Wingedwheel]

Re: Reverse Lock Cam and related parts to shift

DD, before you go any further look up at your shaft coupler. If the splines even look uneven they will keep you lower shaft from turning enough. It would be very difficult to twist that upper shift rod. Forward still works doesn't it?? If you can get the coupler off(heat it first) you can put it on the lower shaft and see how much slop it has. Its an aluminum part and does wear faster than the steel shafts. I just used the process of elimination. Lower unit shifted fine off the engine, upper shift block worked fine, which led me to the coupler.

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift: UPDATE

Re: Reverse Lock Cam and related parts to shift: UPDATE

Well I found the culprit. Inside the MerControl the shift lever had a piece broken off. This was noticed when I took it apart and the piece fell out.

Of course it was broken off on the reverse side, allowing me to shift to reverse, but slipping when I need the extra 1/4" of travel.

Now the hunt begins to either A) find a new shift lever or B) find another MerControl.

The shift shaft did have a slight bend/twist in it that I also managed to take care of (without removal and the use of visegrips). I can now shift normally into F-N without any chatter. R will engage if I give it a little nudge at the motor.

Thanks for the help. Will update if and when shift lever has been replaced or fixed.

 

[egclassic]

Re: Reverse Lock Cam and related parts to shift

DD, before you go any further look up at your shaft coupler. If the splines even look uneven they will keep you lower shaft from turning enough. It would be very difficult to twist that upper shift rod. Forward still works doesn't it?? If you can get the coupler off(heat it first) you can put it on the lower shaft and see how much slop it has. Its an aluminum part and does wear faster than the steel shafts. I just used the process of elimination. Lower unit shifted fine off the engine, upper shift block worked fine, which led me to the coupler.

If your shaft coupler is worn, I would look for the cause. One of the two shafts(upper or lower) would have to be binding and not turning as freely as the other for the coupler to wear.

 

[ddiggerr]

Re: Reverse Lock Cam and related parts to shift

I managed to find 2 MerControlers for $50 with all wiring and cables. Problem solved. Reverse is back and works flawlessly.

My guess is the previous owner was the cause of the problem as the bottom fin(not sure of the correct name) of the LU has a piece broke off from possibly hitting something.

Thanks for all the help.