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1965 500 - No Reverse

bill_w

bill_w

Advanced Contributor
I just bought this 1965 50 hp (serial 1867937), and there is no reverse gear. Before I start tearing it down, is there anything in particular I should be looking for? I did check the cable linkage, that seems to be OK. When in forward, the prop ratchets in one direction, like it should. In reverse, there is no ratchet, the prop just spins freely in both directions, same as in neutral. Any ideas would be appreciated.
 
Has anyone had the lower unit off for waterpump work ?????------------Take it off again------------------Put lower unit in forward ----------Put controll in forward and re-assemble. ----------This is quite common after water pump impeller replacement.
 
hey bill no expert but i did as the first gentleman said and if you are off by a tooth that could be your problem, i have a 50 hp merc 500 1971 and i wasnt that lucky,through the years of grinding into reverse from the guy i bought it from, it wore the reverse gear to nothing and these old mercs are a nightmare to try and get parts for. i hope you have better luck than i did and seeing you are from pickering dont bother looking in belleville thats where i am from and theres nothing down here. i wish you the best of luck and hope this helps
 
Getting used parts is just a matter of knowing where and how to look.----------In some areas used parts are plentifull.
 
The previous owner did have the lu apart..because it had no reverse when he bought it. He mentioned something about a brass piece (he called it a pinion, but he's not a mechanic) that didn't line up. Sounds like that's what you are saying...something just not aligned. I'll find out this weekend, and let you know.
 
There is a cam that operates the reverse lock-up.----------If that is not on correctly it will also cause shifting issues.-----------The lock mechanism must also be free to move and not jammed up.
 
OK..got it tore apart. I did get it running first, amazed at how quick it started after sitting for 4 years. There is no sign of anything resembling what you show Jeff. I don't know if its missing, or if there was one there. Your pics are different from what I'm seeing. Should the shift rod be able to turn 360 degrees? Mine does, with no sign of locking into reverse. A50 Merc LU 003.jpglso, it was a good thing I took it apart. When I had it running on the muffs, there was hardly any water from the pee tube. Who ever had it apart the la50 Merc LU 001.jpgst time didn't replace the grommet from the pump to the water tube, so hardly anything was getting to the head. Pics attached show what I am looking at.50 Merc LU 002.jpg
 
Sorry, don't know why the pics came out that way. First time I've posted pics. Anyways, what next guys? Tear the gearcase apart?
 
No! Take some Vise Grips, gently clamp them on the shift shaft, and turn it CCW. The first 'bump' you feel will be neutral. Confirm it is in neutral by rotating the prop shaft. Then turn it a bit further. THe next 'bump' will be reverse. If you turn it too far, you'll have to keep going CCW until you get neutral again.

This is a later LU than what I thought you had--sorry for the confusion. That said, there IS a part missing, a black plastic cam that works the neutral/ reverse hold down lock.

Jeff
 
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Hi Jeff OK, tried that. From forward gear, about an 1/8 of turn CCW puts it into neutral. Another 1/8 of a turn CCW puts it into a second neutral. I can feel the bumps/detent positions. Continuing to turn it CCW, about 3/4 of a turn puts it back into forward. If I spin the prop in neutral, it pops into forward by itself. Is this what the plastic cam prevents, and is it spring loaded so it fits into the two grooves on either side of the shift rod, seen in the first pic? I'm off the wall guessing here, but I figure those grooves are there for a reason. I don't have a parts diagram for this engine, but I'm looking at one for a 402, and it shows a washer, a spacer, then the reverse cam lock, in that order from the gearcase oil seal up. The rubber washer is there.

When the shift rod is in the reverse position, the prop is no harder to turn, there's no grinding, so I think the reverse gear must be OK, and not stripped off? The shift rod will turn in either direction, and the results are the same. Maybe the shift dog is stripped off? Sorry for so many questions, but I've never torn a Merc apart. Old split case OMC's, even the evil old 60's OMC electo-magnetic shifts, but never a Merc. I can read a parts diagram, and can see how the shifter works, what pushes on what to get gears engaged. It seems like either something is broken, stripped, misassembled, or just missing in there, and the shift dog isn't going back far enough to grab reverse. I think it's time to learn about the innards of Merc gearcases!!!
 
I may have the reverse cam. Along with this motor, I got a complete (minus gearcase) '68 500, and a box of parts, that I never really went through. I did see 1 starter, 2 mags, an old Evinrude starter, and a whole lot of small parts. I'll look through it this weekend, now that I know what it sorta looks like (small, black, plastic, with a hole in it). The parts section here call it a reverse cam upper and lower, I think thats what my book shows as spacer and reverse cam lock. Too bad there's no pics of them.
 
What do these parts do anyways? If reverse is engaged by the shift rod, and held there by the cable from the control box, what does the cam lock do?
 
The spacer is just that and the reverse cam lock locks the motor down while in reverse to stop it jumping out of the water.When you put the shift in reverse the lock rod is forced up the ramp which in turn moves the locking hooks down on to the tilt pin
 
Gotcha. It has nothing to do with the gearcase going into reverse. Ok, I can live without it, if I don't have the parts. Just don't rev it in reverse (if I ever find reverse). I never run my Evinrudes locked down. I did wonder why I could tilt the motor up in forward. So, its back to tearing down the case to find out whats going on (or not going on) in there.
 
Okay, I finally tore down the gear case. It has been apart before, and sorta butchered. The cover nut (big plastic threaded ring that holds the carrier in) is broke in half, they tried to hold it in with locktite. Obviously, that didn't hold, and probably when they tried reverse, it just pulled the whole carrier away from the drive pinion, so no reverse. I think if I get another cover nut, and tighten it in to spec, I should have reverse. My book for the 402 specs out a 'tab washer', that you bend a tab up on to hold the nut in place. I don't have one, just a thin brass washer that goes where my book says the tab washer should be. Anyone know if thats right? I searched through my box of parts, and did find the spacer for the reverse lock, but no cam. Again, no biggie, just don't rev it too high in reverse. So, now to find a cover nut!!!
 
bill_w said:
I just bought this 1965 50 hp (serial 1867937), and there is no reverse gear. Before I start tearing it down, is there anything in particular I should be looking for? I did check the cable linkage, that seems to be OK. When in forward, the prop ratchets in one direction, like it should. In reverse, there is no ratchet, the prop just spins freely in both directions, same as in neutral. Any ideas would be appreciated.
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Hi. I have the same motor and I have just figured out a fix for your issue. I put a couple of washers between the follower cam and slide cross pin (#'s 52 and 53 in the Gear Housing Assemby diagram of the Merc 500 manual). Good luck.
 
With that plastic nut broken, the reverse gear and bearing assembly will move aft and the dog clutch will not be able to engage reverse. That's the problem.

Good sleuthing! Be sure to put a new impeller in.

Jeff
 
I did find the cover nut, screwed that up tight and had no more shifting issues. I didn't bother fixing the reverse lock. Sold the motor and the 2 parts motors I also had 3 years ago. Now running big OMC's, 225 hp and a V8 275 hp. :)
 
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