Vibration/Shifting Problems

[AguaSki]

My motor is a 1978 Johnson 140hp. Over the winter I replaced my water pump. I also changed my gear oil. Went to the lake yesterday for the first time this year and it felt like I was not going 100% into gear, but the prop was spinning freely and moving the boat nicely. There is a clicking noise and a vibration. The noise and vibration go away when I shift back into neutral. It seems like I am about 90%-95% in gear, but not 100%. This is the same for forward and reverse. The noise and feeling that I am not totally in gear did not exist prior to having the lower unit down for the water pump replacement. In looking at my service manual I noticed a sentence about the shift rod adjustment, ?Thread shift rod into shifter detent until seated, then back off two or more turns until offset faces rearward.? I did not notice this sentence in the manual when I had the lower down over the winter, and I would just spin the shift rod in the direction I needed so I could reconnect it under the motor. Now I am wondering if my shift rod is out of adjustment. Do my symptoms match my theory? Can I compensate by making adjustments with my shift cables? The cables are only a couples seasons old.

 

[CharlieB]

Re: Vibration/Shifting Problems

While it may be possible that your shift rod adjustment is not perfect, the gearcase is locking into both forward and reverse gears.

Generally an incorrect setting will not fully lock into ONE gear.

Vibrations are often caused by any of a number of things, most commonly, a bent prop or propshaft, worn bearings, plug fouling on one cyl, ignition failing on one cyl. loose/worn motor mounts or bushings.

For your own peace of mind ou may elect to re-install your LU to perfect the shift rod adjustment. Do not be surprised to find your vibration still exists.

 

[tashasdaddy]

Re: Vibration/Shifting Problems

99% you are correct. drop the lower and get the height correct.

 

[AguaSki]

Re: Vibration/Shifting Problems

Been a busy week and I just got to dropping the lower unit. Problem is, I don't think I can get out to the lake this weekend to verify my adjustment worked. After dropping the lower unit I screwed the shift rod in as far as it would go. It took 4 revolutions to screw in all the way. The shift rod height should be 21 53/64. I don't have anything that can measure that accurate, but I did use my tape measure that is good to a 1/16 inch. Should be somewhere between 21 13/16 and 21 7/8 on my tape measure. I know there is a special OMC tool, but I am hopeful I can get away with a just a tape measure. 4 revolutions out seemed to measure a hair short, so I backed out one additional revolution for a total of 5 and put everything back together. 5 revolutions out seemed to be spot on with the tape measure. Do you think backing out 5 revolutions is enough? Seems that the manual should be able to quote the number of revolutions to back out the shift rod instead of providing a length spec. Hopefully I can test the adjustment next weekend, but I would love to hear anyone's experience with making this adjustment before I head out to the lake. Nothing worse than showing up at the lake and finding out you get to drop the lower unit again.

 

[tashasdaddy]

Re: Vibration/Shifting Problems

i use a tape measure also, and get as close as i can. all you can do is give it a try.