Twice now this summer I have found the two nuts against the cotter pin and the prop slipped back against them. The last time was after hitting a log in the water, so I hauled the boat, put on the spare prop (thinking we dinged it on the log because of the vibration felt immediately after the hit) and tightened the nuts. Now after hitting nothing I feel some vibration again, so I went under the boat and found them back against the cotter pin again. So maybe the first prop is ok, it was just vibrating because it was not tight on the shaft.
Anyway, how can I tighten the nuts so they don't come loose? (My method last time was to put the first nut on, hold the prop with my gloved hand and tighten as much as I could, then repeat with the second nut.)
Not wanting to start a large-nut-first vs. small-nut-first argument, just a simple how to tighten question....
After you tighten the first nut, you need to keep a wrench on it and tighten the second nut against that. That is why the large nut goes first. Unless you have a line wrench that big.
Vibration could be due to shaft end being bent. BTDT, different log.
I wedged a 2x4 under the prop to get as much leverage as possible to tighten the first nut. The used a couple big wrenches to tighten the back nut. Mine never loosened this way.
If you go the wood block method to chock the prop do so in tight at the hub. If done out on the blade area it could twist the blade.
I agree with Steve. I put a 2 x 4 between a prop blade and the hull and then really moose on the prop nut. I usually use a 15" Crescent wrench. I'm a big boy, and I'm guessing I get about 100 ft/lbs of torque on the nut. I have never bent or damaged anything. When I have attempted to straighten a bent prop blade or shaft, I have to use a hell of a lot more force than I can exert with a wrench. You can easily bend aluminum blades, but bronze is a different animal. By tightening the prop nut by merely holding the prop from rotating by hand, you'll never get the prop nut tight enough.
BTW, if your cotter key is riding up on the machining radius at the strut end of the keyway, this would keep the prop from seating properly on the shaft and could also explain your vibration.
I actually had the opposite problem, the key was stuck in the groove. Got it out and cleaned it up until it fit snugly but not loose. With the key out, I slid the prop up to where it would go no further, then marked that spot with masking tape. Put the key in, slide prop on to make sure it goes to the tape, then put the nuts on.
I'll do it again with a wood block to hold the prop. Thanks for all the input.
I am so glad I have a castellated nut and pin.
Blue locktight worked for me.