RPMs increase while power decreases, not the prop

[2strokesmoke]

If that's the case, he's probably missing that large "spacer" (round like a washer, but much thicker and machined to fit into the hub and prop shaft).

I'm batting 0 for100 trying to interpet posts so......


Part #19 or 20 at this parts fisch(I don't know his model # but should be close enough)

2000 T9.9ELHY Yamaha Outboard LOWER CASING DRIVE 2 Diagram and Parts

For the OP, can you post your model # and or check under your prop and see if you have the parts as shown in the parts fisch ^^^?

My motor is the 9.9MSHY. In my case it would be items 15 (spacer) and 16 (washer plate). I will verify the parts when I get home although i doubt they're stamped with a p/n but I think I have back ups of both still in the Yamaha packaging and if so I'll compare the two side by side. I'll also post pics of the pin and how when installed is too far to fit in the grooves of the nut without backing the nut out. I'll get pics of whatever spacer and washer parts I do have as well.

2000 9.9MSHY Yamaha Outboard LOWER CASING DRIVE 2 Diagram and Parts

Also, my prop is one of the ones listed below. I believe the one I underlined but I'll have to verify. Same for 9.9 and 15. If I remember right, when I changed from 9.9 to 15 I went one pitch up from what was on it from the factory (I know that statement doesn't tell much)... even still these are all listed to be used with my motor.


A AMITA 3

9.9, 15

3 9.25 7 R 3111-093-07
3 9.25 8 R 3111-093-08 3 9 1/4 8 R 683-45947-00-EL
3 9.25 9 R 3111-093-09 3 9 1/4 9 R 683-45945-00-EL
3 9.25 10 R 3111-093-10 3 9 1/4 9 3/4 R 683-45952-00-EL
3 9.25 11 R 3111-093-11 3 9 1/4 10 1/2 R 683-45943-00-EL

[2strokesmoke]

Torque the prop nut on the shaft to spec's. If the grooves in the nut don't align, tighten slightly more till they do- This is per the Yamaha SHOP manual

I'll need to find the torque spec for sure so I know I'm on the money. However, I can screw the nut on with just my fingers enough to get the pin to set in the groove of the nut. Any slight tightening with a socket and the pin is too far from the nut... which would indicate I am missing the washer, spacer or the wrong prop is being used. I'll get pics up of all this later today.

[TownsendsFJR1300]

I'll need to find the torque spec for sure so I know I'm on the money. However, I can screw the nut on with just my fingers enough to get the pin to set in the groove of the nut. Any slight tightening with a socket and the pin is too far from the nut... which would indicate I am missing the washer, spacer or the wrong prop is being used. I'll get pics up of all this later today.

Looking at your parts fisch, simply adding another outside washer, part #16 (or two) won't hurt anything and will bring that nut out some so the cotter pin actually engages. I'd get the OEM part, just so a cheaper off the shelf washer, doesn't rust, etc... That prop hub may be a knats hair shorter than how Yamaha machined the prop shaft...

There's a spec for the torque but pretty much just snugged down good n tight works.

Right now, is the prop tight to the shaft? It, of course, shouldn't be loose.

I would, as 99 Yam posted, mark the hub with the prop and check for any spin/failure. That's what it sounds like.

As a side note, I have a prop lock that strictly uses a nylon retainer in the "nut". You use a "key" that fits into the cylinder to tighten / loosen the nut.
No cotter-pins, etc. No issues either, (9 years old)

[2strokesmoke]

Looking at your parts fisch, simply adding another outside washer, part #16 (or two) won't hurt anything and will bring that nut out some so the cotter pin actually engages. I'd get the OEM part, just so a cheaper off the shelf washer, doesn't rust, etc... That prop hub may be a knats hair shorter than how Yamaha machined the prop shaft...

There's a spec for the torque but pretty much just snugged down good n tight works.

Right now, is the prop tight to the shaft? It, of course, shouldn't be loose.

I would, as 99 Yam posted, mark the hub with the prop and check for any spin/failure. That's what it sounds like.

As a side note, I have a prop lock that strictly uses a nylon retainer in the "nut". You use a "key" that fits into the cylinder to tighten / loosen the nut.
No cotter-pins, etc. No issues either, (9 years old)

I just cant imagine it would be the prop, it was nearly new and the second one I put on was brand new and had the same issue... still worth checking though and I will for sure. A prop for $55 could be a you get what you pay for type of deal!

No, the prop is not tight to the shaft. I mean, the splines or whatever are solid when you slide it on but once the prop nut and pin are on you can push and pull the prop in and out probably and eighth of an inch.

I'll have to check out the nylon prop nut.

[TownsendsFJR1300]

In any case, the prop should be bolted tight to the prop shaft.

If the prop shaft ITSELF has play, that may be another issue. My
prop shaft does not move in or at all. There are specific clearances for backlash, etc. If the prop shaft itself goes in and out 1/8", I strongly suspect there's an issue in the LU.

Re the slippage, if there was damage inside the LU, I'm sure you would hear gears grinding.

**You may try tying the boat to dock REALLY WELL (use common sense as this can be very dangerous) or leave the boat on the trailer (even with the rear towing strap attached) and test on the loading ramp partially in the water. Slip into forward and putting some load on the prop / motor listening to the LU. See if it rev's to full throttle (which it shouldn't when tied up and in gear).

To my knowledge, with what you've posted, it doesn't sound like much else.

And lastly, to clarify, the 1/8" play, is that the prop moving on the shaft OR the prop shaft moving in and out of the LU?

[2strokesmoke]

I was wrong about the back and forth play in the prop, not sure what I was remembering. There is no play even when the nut is hand tightened. I pulled the prop, washer and spacer and all is good. I compared them to the new parts I have too and all looks good. The props I have are the #10 pitch of the props that work for my motor.
The third pic is of the nut hand tightened and the fourth is after I tightened it snug with a socket. Starting to sound like marking the hub and prop is a must, although again I've got two of the same and one of which I've run for many hours without issue and with the same load, boat and everything.
Ignore the other washer in the bag, it goes with the thermostat.
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[TownsendsFJR1300]

Your last two pictures are fine putting a cotter pin in there, it isn't going anywhere..

If you feel more comfy, put another factory washer under the original (to space the nut back farther).