lower unit going bad?

mookieo2

Petty Officer 3rd Class
Joined
Jun 12, 2002
Messages
84
Finally got my 89 120 working great. When underway every once in a while there is a slight bang from the motor. it doesn't happen at any set RPM just randomly. Is the lower unit clutch going bad? How long until its totally shot and needs a rebuild?
 

kmarine

Chief Petty Officer
Joined
Nov 5, 2010
Messages
581
Did you check the outdrive oil or change that It is recommended annually normally when winterizing. was the oil milkey or solid green oil. you may have water in the oil. have pressure tested or serviced if not sure.
 

mookieo2

Petty Officer 3rd Class
Joined
Jun 12, 2002
Messages
84
I changed it recently when I got the motor running good. This was the first time I took it out for the day besides testing it for a few minutes here and there. The lu fluid was black when I replaced it. I also adjusted the shift cable because it wasn't going fully in neutral. I could hear a slight ticking when I spun the prop by hand. The lever on the motor side wasn't fully pointing down. Maybe the cable is stretched/stretching out. It goes in neutral now fully.

Should I check the fluid again?
Should I pull the LU and check the shift rod height?
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
The random bang like you hit something is characteristic of a worn clutch dog/forward gear. Improper shift adjustments certainly will contribute to premature wear. But once it is worn, there is no way to restore it other than parts replacement. And every time it bangs, the wear greatly increases. The banging also can damage the shifting mechanism.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
Remove lower unit and check shift rod height as removed.------Then adjust it if it is wrong.-----Test motor again.
 

mookieo2

Petty Officer 3rd Class
Joined
Jun 12, 2002
Messages
84
Does anyone know what the shift rod height should be for this motor. 1989 120 Johnson?
 

mookieo2

Petty Officer 3rd Class
Joined
Jun 12, 2002
Messages
84
will a lower unit from a 1978 140 fit? I have one from my 140 that ate a set of rings.
 

pckeen

Commander
Joined
Jun 20, 2012
Messages
2,067
Check a parts diagram for the two motors - marine engine dot com has them
 

mookieo2

Petty Officer 3rd Class
Joined
Jun 12, 2002
Messages
84
I adjusted the shift rod to the recommended height of 21 15/16. When I first removed it and measured It It was in forward so I don't kn ow what it was originally. I didn't realize that when re-installing the lower unit the shift rod would spin. I did two trips on it since I adjusted it. One in the ocean in some decent surf and another to dive somewhere about 10 miles away with two other people. It hasn't banged yet. I hope it holds for a while. I picked up a used lower unit on Craig s list for cheap as a back up.
 
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