McGard Prop Locks?

[rpr]

I used a tamper proof McGard prop lock on my old ProXS to prevent someone from walking off with my prop. However, the nut was very loose every time I swapped props on the motor. I’m now setting up a new boat with a 300HP Verado and an expensive prop and I’m tempted to use a McGard again but I’m nervous about it.

Mercury’s OEM prop nut kit uses a beveled washer and a nylon lock nut to prevent loosening. McGard’s system replaces the nylon lock nut with a tamper proof nut but as far as I can tell it does not use nylon to prevent loosening, so the whole system relies on a beveled washer. This did not work on my ProXS.

Does anyone have any good/bad experience with McGard?

[21XDC]

The loosening is from thrust washer wear. Not the nut loosening. You might not be tightening the nut to specs, and if you are, You should be re torqueing the nut now and again.

[Cajun Pop]

Mine came with a Bellville washer that goes between the prop and the nut. If that is installed and tightened until the washer flattens out and the nut still loosens up, you have a really worn thrust washer. If the Bellville washer is not installed, the nut can loosen even if it is torqued pretty tight. Ask me how I know.

[rpr]

What exactly do you guys mean when you say “thrust washer”. Mercury does not use this term for any of the fat shaft solid hub components. Mercury’s diagrams refer to a “1.5” washer”, a “1.5” cupped Belleville washer”, a “1-13/16” thick washer”, and the “hub”.

I assume you’re referring to the 1-13/16” thick washer? However, this washer is just a flat, smooth steel washer, as far as I can tell it’s not designed to prevent loosening, so I’m not sure what could wear on this that would cause the prop nut to loosen.

[21XDC]

The prop lock uses a Belleville washer that says "This side UP" right on the washer. Did you read the directions?

[Savage]

Racing hub nut torque spec is 55 lb/ft. The nylon in a nylock nut is not meant to maintain the torque spec, it is there so the nut doesn't fall off completely.

[rpr]

Yes, the Belleville washer in the McGard kit was installed with “This Side Up” up. For the folks referring to “thrust washer wear”, can you clarify which component of the hub kit you’re referring to? The 1-13/16” washer that Mercury refers to as the “fat washer”?

Maybe I just received a bad kit/nut.

[21XDC]

The fat shaft hub kit does not have a thrust washer as a seperate piece, It's incorperated into the drive sleve insert. Just re torque as needed.

[Savage]

Tighten with a Torque Wrench this time 55 lb/ft.

[rpr]

Where did I say I did not use a torque wrench?

The McGard prop lock kit was properly installed and torqued, but it continually loosened up on me.

For anyone else using McGard prop locks, I would suggest you routinely check it. I don’t put many hours on my rigs so it loosened up pretty quickly on me.

Thanks for the feedback guys.

[21XDC]

Min 55lbs as paper work says... I have used these prop locks for 15 years w/o any trouble.

[Savage]

Same here. I NEVER had a problem with a properly torqued prop fastener coming loose, on any motor that I have owned.

[rpr]

Ok, so I called McGard to see how they recommend installing their prop lock on motors with the 1-1/4” solid fat shaft hub kit. Their instructions in the kit say to “leave the large thrust washer in place”. But as discussed above the solid fat shaft hub kit doesn’t have a thrust washer in the conventional sense, it has a 1-13/16” “thick washer” that sits directly against the hub. Merc’s Belleville washer then sits on this 1-13/16” fat washer. I installed McGard’s Belleville washer the same way, sitting on this 1-13/16” fat washer.

McGard said this is likely why their nut loosened up on me, they said their Belleville washer should sit directly on the hub even though Merc’s Belleville washer does not.

McGard also said to use their specified 50 ft-lbs of torque, that’s what their Belleville washer is specifically designed for. They said Merc’s 55 ft-lb spec could start to flatten out their Belleville washer.

So apparently I did install it wrong. Thought some others might benefit from the clarification/confession.

[Savage]

On a racing hub I use EVERYTHING in the Mercury hub kit except the nut.