Can't get a forward gear

[mmarino]

I have a 1979 50 HP Blue Band 4 cylinder (Ser. # 5445498) with the lower unit dropped for an impellar change and just recently put back on. I can only vouch for the motor running on a stand, never had it on my boat.

I put both the shift and throttle cables on properly and can get it to shift from neutral to reverse, back to neutral, then into forward and back again as many times as I'd like. I can hear it engage into all gears and feel it as well. When it is in forward, the prop spins in both directions freely while clicking, clicking several times during each rotation. It won't engage into gear though, there is no resistance.

In neutral position, the prop spins freely in both directions. In reverse the prop turns in both directions. There is a lot of resistance while it works against compression and turns the flywheel. I'm not sure if this is normal in reverse, but I know the spinning freely with clicking in forward is not. Can someone tell be where to begin. Is it just a problem with how I reassembled the unit, splines not in synch or something. I'm just shooting in the dark. Searched the forum but did not get a lot of help. Maybe I missed something.
Thanks a lot for helping.

 

[AMD Rules]

Re: Can't get a forward gear

Remove the gearbox again, and bench test it as follows:

Hold the vertical driveshaft with one hand to prevent it from turning then you should see the following behaviors with the prop shaft using the other hand:

1) in neutral the propshaft should turn freely in either direction without resistance.

2) in reverse, the propshaft should not turn in either direction

3) in forward, the propshaft should not turn counter clockwise, but will turn clockwise and 'ratchet' as it slips over the clutch dog teeth



Based on your description so far, I fear you have a genuine gearbox problem. Lets hope not.


.

 

[mmarino]

Re: Can't get a forward gear

AMD Rules thank you for the good information. When following your instructions, with the lower unit removed, how do I get it into all of the gears. Can I turn the shift shaft while holding the drive shaft? If so, what should I use to turn it, socket, a special tool?
Thanks again.

 

[AMD Rules]

Re: Can't get a forward gear

You can rotate the shift shaft with any tool that works. I typically clamp on to the smooth shaft area if you can, rather than risk damaging the splines. Don't turn it very much. You should be able to feel the neutral detent. Forward and reverse are just a bit in either direction from neutral.

Put it in each gear, then proceed to hold the drive shaft from turning and test the prop shaft function.

 

[mmarino]

Re: Can't get a forward gear

Thanks a lot for the quick reply. That's a big help. I'll check it today. Worst case scenario, am I looking at a whole new lower unit replace, or can it be repaired, special tools, etc. I know I'll need a manual.

I'm giving you a loaded question as you can't see inside of it, but if you could make an educated guess, I'll know where to go once my diagnosis has been made.

 

[AMD Rules]

Re: Can't get a forward gear

Thinking you may have some worn internals in that gearbox. Let's wait to see what the bench test reveals.

This is the specific part that has me concerned...

When it is in forward, the prop spins in both directions freely while clicking,

In FWD gear, the prop shouldn't turn freely CCW and should ratchet (click) in the CW direction only.

Your description originally is a bit confusing. Things may be just fine. while you can test the gearbox function while on the motor, I prefer to eliminate the mid-section shift linkage alignment as a source of the problem, by bench testing it.

 

[mmarino]

Re: Can't get a forward gear

AMD, the Gods are smiling on me this day. I ran your bench test and that lower unit passed with flying colors. I'm not sure what is different, but instead of the prop rathceting freely in both directions in FWD, I get resistance in CCW and ratcheting in CW. Amazing. I don't know if this will help, but I found a 11/32 Craftsmen ignition wrench, 12 PT., that fits very nicely over that shift shaft, allowing me to turn it without marring it.

My last concern is reassembly. I'm thinking it should go back together with the lower unit in the neutral position as well as the upper motor case shift lever in the neutral position also? There is a cam that slides down the shift shaft and rests on top. It seems to meet a rod that is spring loaded in the middle unit. I think I know how to position it, but is there a right way?

Thanks so much for staying with me on this. Your help has been a Godsend.
Marty

 

[AMD Rules]

Re: Can't get a forward gear

That great to hear...

In reverse, that cam should be at its highest point under the spring loaded shift lock rod. It locks the motor in the down position. Hopefully the shift lock cam only goes on in one position, but I'll check my service manual.

Factory service manual says to re-install when in forward gear. I prefer neutral because the neutral shift detent on the gearbox keep it where it needs to be. Up to you...doesn't really matter. Just put the upper lever in the same gear position as the lower unit and you should be ok.

If you're having problems getting the drive shaft splines lined up, have an assistant rotate the flywheel a little bit. It should all go together by hand, quite easily.

Good luck.