Thrust Washer issue

[Plan3]

A friend and I recently replaced the prop on my 2002 Evinrude 200 hp. Though a new thrust washer came in the kit, he went ahead ahead and left the old one on, as it seemed in good condition. (I allowed him to do the job all by himself, for experience.) He took the craft out for a trial run and returned, saying that he believed I had a gearbox problem, because when he accelerated beyond 3500, the motor raced out. I told him, I'd have to come and check it out, since I had returned to port at about 1000 rpm after the original spin out. Something else was probably at issue, I believed.
I pulled the prop, pulled the thrust washer, saw a difference between that and the one in the kit, including thickness and a bevel, replaced it with the new one and the problem disappeared.
My friend is not convinced that the mili-meters' difference caused the problem with his installation, despite my theorizing about movement back and forth on the shaft caused by load issues (including acceleration), references to pilot shaft use--for us older under-tree mechanics--when installing a clutch, pressure plate and release bearing roles, the whole works.
I know the Forum has more important issues to address, but If someone could lay out the explanation better, so I could share it, I'd be relieved.
Or, maybe I've got it all wrong!

 

[Chris1956]

Re: Thrust Washer issue

The thrust washer keeps the prop from hitting the gearcase casting. Under load the propshaft will move into the gearcase a bit, so the thrust washer better be thick enough to account for that. Did the new prop have a different (ie modular) hub than the original prop? If so, it would have had a different thrust washer.

As for the motor "racing out". Maybe he had it trimmed too much? There is no scenerio I can think of that would cause that, by changing the thrust washer.

 

[Plan3]

Re: Thrust Washer issue

Chris: Thanks for the reply. I'll pass it on. (As I indicated: the old thrust washer (not taken off the shaft) was considerably thicker than the one in the kit, and it was beveled on one side.) In any case, I believe your answer is to the point and sheds light on the issue. Again, Many Thanks!

Plan3

 

[Haffiman]

Re: Thrust Washer issue

Providing the splines on the prop has been matched with the splines on the shaft, I do not see any reason for the prop to 'spin' out, unless the difference in thrust washer thickness caused a severe exhaust leakage between prop and gear housing.

 

[dazk14]

Re: Thrust Washer issue

Providing the splines on the prop has been matched with the splines on the shaft, I do not see any reason for the prop to 'spin' out, unless the difference in thrust washer thickness caused a severe exhaust leakage between prop and gear housing.

+1^

 

[SparkieBoat]

Re: Thrust Washer issue

yeppers on the exhaust leak thingy... bingo