BalsaBob

My Feedback: (24)

Hi, Need to reinstall the small Woodruff Key on the shaft. Does the small black Thrust Washer go behind the Woodruff Key (against the bearing) ... or in front of it next to the drive hub ?
Thanks. Bob

TheEdge

My Feedback: (788)

I'd say that based upon the parts diagram, the answer is yes, behind the woodruff key. But there's someone out there that will know for sure.
Does the Prop Hub mate all the way up on the engine case when it is behind the woodruff key?

fs-120s-e-manual.pdf

Outrider6

My Feedback: (2)

I don't have an engine in front of me, and it's been a while since I had a drive hub off (fuzzy memories), so I am going only by the picture in the OP. I agree - behind the Woodruff key.

It has to go on the inside. Installed first, then the Woodruff key, then the drive hub. There is no useful purpose it could serve on the front face of the drive hub.

BalsaBob

My Feedback: (24)

Thank you all for the replies.

1967brutus

I know for 100% sure, that indeed first the washer goes on, then the woodruff (effectively locking the washer in place, although that is NOT its function, and then the propdriver.

It is a bit of an awkward construction that can lead to issues, while there is no good reason for the washer: A slightly higher ridge on the prophub would eliminate the need for that washer.

hellcat 1

I know for certain that if the washer isn't behind the key, the engine will not turn over on a O.S. 90 surpass. I bought one for $25 once that didn't have the washer on it. the guy that sold it to me thought that something was wrong with the motor. It had a purpose on that motor.

jaka54

The washer should go on first ,then the woodruff key (that´s why the woodruff key has a cut surface on one side) then the prop driver, then the prop and nut!
Simple as that!

Jesse Open

Simple and very well done

1967brutus

Oh, that washer NEEDS to be there, same on the 1,20. That is not what I meant.

What I meant was that OS for the same production costs could have designed the propdriver such that it would not rub on the front bearing just all of its own.
I mean, technically there is no reason for the designer to use a washer there.

Jesse Open

You can bet O.S. had a reason for employing the washer. Little doubt they weighed the alternatives before making the decision. May not be altogether obvious to all but that is of no consequence.
In manufacturing, moves like this are made often. Could be something as simple as an expediency. Perhaps easier, cheaper and quicker than altering a production machine to provide the needed projection. If not that, something else.
No real need to second guess, they had their reasons to do it that way.