prop nut

I just ordered a ACME 540 prop for my 86 SN 2001. When i put the new prop on, how tight does the prop nut need to be?

thanks for your help
chris

Tighten until the cotter pin will go through. When you spin it in the water it will work its way up the tappered shaft and will have to be pulled off with a puller.

Debur the keyway, then
Lap the prop to the shaft with compound, until the contact patch is at least 2/3 of the bore. Then mark the shaft with a sharpie how far the prop seats on the shaft.
Now add the key, and the prop better seat at the same position, else the keyway is binding..
Don't draw the prop/keyway on with the nut, get it to seat before torqing, and there will be zero err and vibration from installation.
The lapping will also make the prop easier to remove later because the strain is distributed evenly throughout the taper..

I don't know what other boaters have done, but I would use a different nut that will let you also use a cotter pin. The nylock prop nuts are used on propshafts that have an eyelet at the end for a cotter pin to be used.

Use a cotter pin!
I lost a prop by just using a lock nut last summer.

It's a sad feeling to be stuck out on the lake knowing that your $350 prop just sank to the bottom.

Needless to say... you live and you learn....that day I learned why God made cotter pins.

I had a problem the last time I changed props. when I tightened the castle nut it came up way short of the cotter pin hole. I couldn't torque it enough to get it to the hole (or at least I didn't think I SHOULD torque it that much). But if I loosened it enough to hit the previous hole, it was too loose. So, I went with a nylock. I would really rather go back to the castle nut, but I don't know how to get it to line up. I guess I could use a flat washer to shim it? Any suggestions?

Sure, I'd use a washer to shim it up so that u can get a snug fit. It works on airplanes why not on boats. I would use stainless so that it wouldn't rust.

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