1973 Mercury 20hp shifting problem

Joined
Jun 3, 2020
Messages
8
Recently purchased this motor after a running demo with water to a muff. Ran great, shifted great, but needed a new impeller. Brought it home. With the transmission in neutral, removed the lower unit to replace the impeller. After reassembly, it was in nuetral, but would not shift into forward or reverse gear. Removed lower unit again, carefully found neutral with the shift shaft. Reassembled. Now would shift fine, but forward and reverse gear are opposite. How could this happen? I did not disassemble the transmission at all.

Any help on how I could solve this issue would be greatly appreciated.
 
Joined
Jun 3, 2020
Messages
8
Well, I tried the advice Chris1956 had for me, but it doesn't appear to be so simple. Here is more description regarding how it is acting. Looking down at the top of the lower unit, the driveshaft spins CW when the engine is running. With the shift shaft rotated all the way CCW, it is in forward gear. I cannot turn the shift shaft any more CCW. One click CW gets me to neutral. Two clicks is reverse. It will not turn an further CCW than that. Total, I can only turn the shift shaft approx 200degrees. Should I be able to go all the way around? Any advice on what to try next?
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,561
Well, it appears you are trying to adjust the shifter they way I had counseled. When you look at the shift rod, and shift from neutral (gearcase removed), the upper shift shaft turns CW, right? That is why you need to move the lower shift shaft CCW to find neutral.

If she will not go into neutral by turning CCW, you may have some issue with the gearcase itself..
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,897
What's wrong with what you have? Why do you think you need more rotation? The slots in the cam are only 10-20 degrees of shaft rotation apart. You have what you need. Put the shifter in whatever gear you prefer, set the remote/tiller shift lever to the same point and put her back together.

The direction the drive shaft turns has nothing to do with the shifter. One supplies the power the other how it's distributed.
 
Joined
Jun 3, 2020
Messages
8
Okay, so just for some backstory: When I had everything together, but the gears were backwards, I took it out on the lake to see how it would do. With the shifter in Reverse, it would go forward. I took off, and it was running great. Idled good, got up to speed and stayed there. Reverse also worked well too, with the shifter in the F position. Now, as I was cruising along, the motor suddenly revved high, and I lost my propulsion. I quickly slowed down when this happened. Reverse was still working, and if I put the shifter on R to go forwards, it seemed fine, but there seemed to be a point where as I slowly increased the throttle and speed, it would reach a point where the motor would start revving up, but not give propulsion, almost as if the gears were slipping once the engine reached higher RPMs or something. It almost sounded like cavitation, but I know it wasn't. I had to to go very slow all the way back to the landing. I understand that the shift shaft and drive shaft are separate, just informing you because in order to determine what gear I am in when I turn the shift shaft when the lower end is removed, I turn the drive shaft to determine which way the prop is spinning, and subsequently, what gear I am in. It just seems like everything is perfectly backwards. I am not able to find a "2nd neutral" beyond the one it is in. It only seems to shift to R and F to either side of the existing neutral it is in, and I am met with a hard stop when I try to turn the shift shaft beyond Reverse of Forward. Did I possibly do any damage when I was out on the lake and I had issues? The driveshaft looks good, no chewed gears, so I am confused what caused my issue of not being able to deliver the power to the prop..... I have tried that Texas Mark, but when I put the Spindle shaft in Forward gear, and my shifter on the motor in forward gear, and then put everything back together, it won't shift out of Forward. It is as if it is stuck just in that gear.

This is driving me bonkers, and again, I appreciate your help.
 
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