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grinding sound when shifting

Swagonmaster

Regular Contributor
OK, I thought I was out of the woods but not yet. The motor is a 1979 merc 140 that grinds the gears when shifting forward and reverse with the engine running like a car when the clutch isn't pushed in properly, shifts ok when the engine off. After a couple of shifts (sometimes just one) the output shaft locks up, the engine dies because of the load and I have to manually turn the prop to unbind the gears which takes some force to do.
Any ideas anyone?
 
It sounds like you have seriously damaged the unit if you've been shifting into reverse without the motor running you can damage the shifting mech. Is the shift cable properly installed?850-controlsetup.jpgThis is what goes on in a LUlushiftsetup.jpg
 
You must not ease an outboard into gear.----Shifting must be done with a quick firm motion.-----If the propshaft locks up there may be serious issues in the gearcase.-----Step #1 would be to drain the gear oil.
 
I drained the gear oil and there weren't any large chunks in the oil and only minor metal fuzz on the magnet so I think I'm alright there. Am going to refill and do some shift experiments to see if I can give more info on what is happening.
 
Observations so far: shifter seems to work smoothly although there is a very small window where neutral is. The trans will shift only a couple of times before locking up and needs to be released by turning the prop manually. While locked up the shifter is very stiff I guess due to the shift mechanism being bound up. It seems that this is an ez shift unit as it will ratchet when the prop is turned counterclockwise when in reverse. More head scratching to come.
 
Ratcheting occurs in forward - reverse is locked in solidly. Turn the LU shift shaft by hand counter-clockwise until it
stops, then with Vise Grips tight on the bottom of the shaft turn it a
few more degrees CCW until it clicks into a stop, this
should be neutral - check by turning propshaft --
prop should spin freely. DO NOT shift into reverse unless someone turns the prop or the motor is running.
It sounds like the shift cam is worn or the spring is faulty (not likely).
If it functions normally the problem could be with the upper shift shaft (happened to me thru corrosion)
 
A quick question, how much will the average prop turn while in gear and the engine shut off of course? Mine will turn about 1/8 turn and that seems like a lot but it's been 35 or more years since I've owned a boat and the memory fades.
 
I tore the lower unit apart today and while I know that the hardest part of doing a job you've never done before is identifying parts that are worn but is it still useable? I really don't see anything that I would expect to cause the prop shaft to lock up. The shift cam is going to be replaced as it looks like it has some wear and that is the part that I would expect to be involved in a shift problem so that may do the deed but it's as Artie Johnson used to say "very interesting but not very funny".
 
I never had the specific problem but feel that the "clutch dog" is binding or is damaged. My recollection of the shift cam is that the grooves are kinda sloppy looking. Surely if the shifting cam and the engagement pin inside the prop shaft, don't set the clutch dog to the right position, shifting could be irregular. Additionally for an engine of that vintage, the spring behind the pin (inside the prop shaft) may be weak.

Not sure as to your definition of "grinding noise" but rpm needs to be high enough for the engine to continue to run when at idle and shifter is engaged yet be slow enough for engagement to occur without "grinding". On my later model engines the manual calls for 675 +/- 50 rpms with the boat in the water, free to move, in F gear. I had an '88 115 Tower but forget the exact number for that engine. And as others have stated, snappy operation of the shifter...by you is the requirement.

The fact that you only had fuzz-metallic paste on your drain plug magnet is encouraging. You'll have that.....the reason Merc. put it there in the first place.
 
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Actually I tend to think that the gear grinding or clatter is being caused by too high of an idle, it seemed rather high just by ear. Looking at the wear patterns of the gears indicates that the reverse gear flat engagement portion has a lot of scuffing which might be normal but could could be why the prop shaft is getting locked up. The only way that would happen though is if the shift cam is not able to rotate out of the reverse apply position so I'm going to have to check to see that the shift rod is really turning the shift cam out of reverse.
 
You are onto the problem: "...wear patterns of the gears indicates that the reverse gear flat engagement portion has a lot of scuffing...". If you don't have a tach, just turn the knurled idle knob down till the engine won't stay running when shifted into F gear in the water, boat moving. Then turn it back in a half turn or so.

If the LU is still apart, I'd take a file to any burrs but vertical surfaces need to be as much vertical to vertical engagement surface as you can get. Otherwise, hard reversing could pop it out of gear...had that happen on a Mercruiser outdrive.
 
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BTW, faztbullet you wouldn't have a part # for the new style cam would you? I don't want to get an old style by mistake because I don't recognize which is which.
 
CAM FOLLOWER KIT 44532A1



Z
[SUB][/SUB]


 
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I wonder why a new spring isn't included in the kit? Since you have access to new and old, what are the differences, and at what year model were the new followers included in OEM production. Thanks.

More thoughts: Also, why no new cam itself, especially since one would expect the change would be/include a more secure fit of the follower pointed nose into the indentations in the cam so if you change the follower why not the cam also...makes sense to me?
 
I was also trying to see a reason for an upgrade to the follower and all I can think of is that the engineers wanted to reduce any friction that might come up because of rotational forces from a shift cam that might not push precisely straight as this would increase shift effort and wear on the cam surface. Since the cam seems to last a long time anyway they may have decided that the follower is at fault rather than the cam although it is possible that tolerances on the cam face may have been looked at also.
 
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I wonder why a new spring isn't included in the kit?
Cause its preloaded to forward and is only compressed in neutral and reverse...these don't wear out
Since you have access to new and old, what are the differences, and at what year model were the new followers included in OEM production. Thanks.
The balls allow propshaft to spin with less rotational force on follower pin...started around 1985 in I4 motors
I was also trying to see a reason for an upgrade to the follower
The nose of the follower will wear down and cause reverse gear engagement issues as not long enough to push clutch dog rearward
 
Faztbullet, thanks for the reminder to think things through when diagnosing a problem. I was concentrating on my shift problem and forgot to think what was happening to the whole system when it was working. Sure I am new to boat engines but as a tech for many decades there is no excuse for not thinking a problem through. It's a good example for everyone else of what a tech has do to come up with answers. Thanks for the help.
 
Cause its preloaded to forward and is only compressed in neutral and reverse...these don't wear out

The balls allow propshaft to spin with less rotational force on follower pin...started around 1985 in I4 motors

The nose of the follower will wear down and cause reverse gear engagement issues as not long enough to push clutch dog rearward

I can just imagine the condition of the shift cam if the hardened follower wears out!
 
Cause its preloaded to forward and is only compressed in neutral and reverse...these don't wear out

The balls allow propshaft to spin with less rotational force on follower pin...started around 1985 in I4 motors

The nose of the follower will wear down and cause reverse gear engagement issues as not long enough to push clutch dog rearward


Thank you sir. Like I keep saying, if anybody knows, you surely do!
 
I can just imagine the condition of the shift cam if the hardened follower wears out!
The groove gets a tad deeper and wider...usually wears due to water intrusion. There are operators that will change their oil monthly as they know gearcase is leaking and not install seals... :confused: :confused:
 
Faztbullet, I am addressing this to you but it is really meant for everyone else since you will know what I am going to say. Up at the top of this thread Quicksilver said something about not shifting into reverse without the engine on or the prop being turned and I thought "why not? everything else can be shifted without a problem" well I found the reason, it bends the shift shaft right at the shift cam. Nothing else, and you might get lucky and have the dogs fall into place and there won't be any problem but I'm glad I had the lower unit apart and was going to replace the shift cam anyway so I was in the area and noticed what happened. So everyone, yes there is a risk to putting your engine in reverse without it running, it's a small thing if you are doing your own work (and catch it) but it would be a rather expensive mistake to make if you are paying someone else to fix your engine and oh by the way it keeps you off of the lake while it's fixed? Oops! So as I said a few posts up: think things through.
 
I was going to throw the bent shift shaft in the punch drawer but thought I'd show you guys how little it takes to loose reverse.
 

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