Mercury 500 (50HP) shift shaft alignment

[mmf]

I am changing the lower unit from a short shaft (16") to a long shaft (20").
My mercury is a 50HP 4 cyl. "500", 1968 model, serial #2407450. I have read alot of posts about shifter alignment on the forum and concerning the reverse lock cam on the site, but I need some more info. I do not have a mercury control box for this motor yet so I am aligning by the motor lever only. I have a clymer manual for this motor but it is also "incomplete".
My main concern is where the "actual" forward-neutral-reverse position is
when moving the shifter shaft. I will describe my lower unit shifting details:
my shifter shaft will rotate in an arc of approx 90 degrees. When viewed from overhead of the removed lower unit, if the shift shaft is turned completely CLOCKWISE, the unit is in forward (propeller moves clockwise when viewed from rear of propeller), then, as I rotate the shifter shaft COUNTERCLOCKWISE I come to a spot that appears to be neutral but has no detent. Turning further COUNTERCLOCKWISE, I come to a spot that is reverse, continuing turning COUNTERCLOCKWISE I come to a spot with a audible click and a detent that is definately neutral. Turning some more past this position going COUNTERCLOCKWISE, I find forward again at the end of the arc. My question is, which one of the positions should I use for alignment?
Also, correct me if I am wrong but I think that the shift linkage on the port (left) side of the power head moves as follows: when in forward, the linkage is towards the front of the motor, when in neutral it is in the middle, and when in reverse the linkage is moved towards the rear of the motor, is this correct? I need that info to correctly line up the reverse cam.
Sorry for the long post but I need HELP!......thanks

 

[Yepblaze]

Re: Mercury 500 (50HP) shift shaft alignment

I prefer to use neutral. The shift shaft will have found the detent and the prop will spin freely in both directions. There is only one neutral. Of course the thing will pop into forward once or twice while I try to assemble things. But that's what I use.

About the shift mechanism on the motor. Roughly halfway through this mechanism's travel is neutral.

 

[mmf]

Re: Mercury 500 (50HP) shift shaft alignment

well, I just looked at my Black Max 150HP and it shows FORWARD towards the front of the engine, NEUTRAL in the middle, REVERSE at the rear of the engine.

I hear what you are saying about setting in neutral.......my problem is I can find 2 neutral positions! If I was to set it up on the neutral position that has the click, my reverse lock cam would be backwards! If I was to set it on the neutral that does not have the "click" then the reverse lock would be right. Hmmmm........maybe I am answering my own question? confusing..........
Did Mercury make a reverse lockout cam that had the "ramp" set up for the opposite side?

 

[Yepblaze]

Re: Mercury 500 (50HP) shift shaft alignment

You may just be confused. Take a break and give it a logical overview as you think about it.

In forward clockwise from above(I'm pretty sure the crank turns that way) the prop should ratchet/freewheel in a forward thrust direction. Or push against you hand well enough as the input shaft is turned.

If it still does not figure out, and you are certain it is backwards, it is possible for a person to assemble the cam in upside down.

I had received one that way and the previous owner had done all he could to run it that way, but the reverse throttle stop left it unable to go. I had to tear the guts out of the lower, lift the shift shaft and reach in ther and turn the cam over.

But that's a big long shot.

Make sure before..........

 

[emckelvy]

Re: Mercury 500 (50HP) shift shaft alignment

The first "Neutral" position you described above is the only correct position, regardless of whether you feel a real "detent" or not.

The 2nd one you describe, when moving the shift shaft even more CCW from Reverse, is merely the shift plunger 'falling' from the top of the Reverse Ramp, all the way back to Fwd. Naturally, along the way it's going to encounter a "Neutral" position but that is just a momentary transition and not the "real" Neutral.

Note that it's not really a good idea to rotate the shift shaft CCW past Reverse, the mechanism was never designed for this. And definitely don't rotate the shift shaft CW to try and shift back into Reverse, once you've hit Fwd.

So, use the 1st Neutral you encounter when shifting CCW from Fwd gear as your alignment position.

HTH.......ed

 

[mmf]

Re: Mercury 500 (50HP) shift shaft alignment

I want to thank you both for your help. I did put the lower unit on this evening and used the "first" neutral position as I had described it. After tightning all the bolts I moved the shift lever on the power head through it's range and found Fwd-N-Rev and spun the prop to check.

I sure would have thought that the Mercury shift cable would have extended
rather than retract when in the forward position. The cam in the shifter box must work backwards than my thinking..........

 

[GrewSS140]

Re: Mercury 500 (50HP) shift shaft alignment

I want to thank you both for your help. I did put the lower unit on this evening and used the "first" neutral position as I had described it. After tightning all the bolts I moved the shift lever on the power head through it's range and found Fwd-N-Rev and spun the prop to check.

I sure would have thought that the Mercury shift cable would have extended
rather than retract when in the forward position. The cam in the shifter box must work backwards than my thinking..........

Thank you as well,I bought a boat last summer with a Mercury500 on it.And when i first took it out on the water i had the same problem.The guy before me had told me that he had changed the water pump prior to my purchase at the end of the season.My educated guess was that someone had moved the shifter lever prior to reassembly and messed things up.I always like to put the shifter into forward before dropping the lower unit as a reference point so that when you put things back together you can always turn the prop a bit by hand if the drive shafts dont mate up properly.But thanks for pointing out the positioning as it will take a lot of guess work out when i correct it this spring.

 

[merc850]

Re: Mercury 500 (50HP) shift shaft alignment

If you think of the design aspects, having the cable and clutch components under no tension while in FWD 99% of the time makes better sense than under tension 1% of the time in N and REV.