What makes the inner prop nut and the outer come loose? How do I reset them to be sure this does not happen again
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https://www.seattleyachts.com/news/clearing-up-the-confusion-of-prop-nutsWhat makes the inner prop nut and the outer come loose? How do I reset them to be sure this does not happen again
Tech, that’s how it is set up, halfnut first. Two wrench’s to set them.
But what makes them come loose? Vibrations?
That's the post I was looking for when I posted the above thread.Shaft nuts coming loose can be caused by a host of issues which need to be identified and corrected.
I posted this in another thread -
In theory there should be no nuts required if everything is fitting correctly. If the nuts have loosened more than once you have other issues that need to be corrected. If this is the case then:
- Disassemble and remove the prop from the shaft and inspect everything. Especially look for cracks and deformations.
- Make sure there is no rotational play between the prop and shaft - the key and keyways are tight.
- Cleanup the prop bore and shaft and using machinist dye check the fit between the prop and shaft.
- Lap the prop to the shaft as required and re-check with the dye. After cleaning up the lapping compound/dye then re-fit the prop and scribe a prop location (index) mark on the shaft without the key installed.
- Reassemble dry (no lube at all) and clean with the key installed and make sure the prop installs to the index mark.
- Get new nuts and install the thin nut first (no lube here either). I use a 3 foot breaker bar and put all of my 172 pounds of weight against it. That's right at 500 LbFt for my 2.5 inch shafts.
- Check that index line to make sure it remains as was after lapping. If it is not in the same location the prop is cracked and will require replacement.
- Put the thick nut on and torque the same then install the cotter pin.