Prop lock question

Hi all. Anyone use a McGard prop lock on their motor?? Last summer I lost the prop on my boat not sure what happened….if the cotter key failed or if someone was in the process of trying to steal it and got scared off after getting the key out….either way, doesn’t really matter now. Got a new prop and was thinking a prop lock would prevent that from ever happening again but I have a question. The pic on the package shows the lock nut going on top of the stock prop nut with the cotter key but the instructions clearly state to remove the cotter key and prop nut then install the prop lock nut. What will keep the prop lock from eventually working loose and just spinning off?

I looked that up and the way I see it is there is enough room in the hollow of the nut for a cotter pin,hence the cut outs on the cap.
a cotter pin does not have to be through the nut to be effective as its only purpose is to keep the nut in place if it were to come loose.

I’ll have to check that I didn’t spin the lock nut on far enough to see if the cotter key hole was exposed. They for sure will not both fit like the packaging shows, it’ll have to be one or the other.

as you have guessed there is no room for both, that pic is very misleading but I have to take it that it was intended to be a pictorial for removing the old nut and replacing it with the lock nut,not stacking them.

I have them on both of my outboards, the lock nut replaces the original nut.

I use one. As mentioned, they replace the existing nut.

No cotter pin required. They use a special locking washer that is concave and must be applied in the correct direction. Two seasons without losing a prop.

Now that you mention it, I suppose I should look into replacing that washer at the end of this season. Not sure how many times it can be removed and retorqued without losing tension.

Edit, there is an installation video showing the nut going on with the washer. I didn’t have the sound on when I just watched but I assume he explains it.

Thanks for the link to the video. Do you check the tension on the nut a few times a year to make sure it stays at 50lbs?

I’ve run a lot of years with the regular prop nut and cotter key combo and never lost a prop until last summer, it feels less secure to put something on that is only using tension to hold the nut in place. It must work though or people wouldn’t buy them and they’d be out of business.

50lbs? You’re supposed to use a torque wrench? Ha.
I haven’t even done that. Made it tight and left it there for the season.

Don’t you go jinxing me.