# Torque wrench for prop nut?



## rovster (Aug 21, 2018)

Seen some recommend, some don't. Going to try a different prop eventually don't want to screw something up. What say you? It's for a Merc 115 ProXS. If torque wrench required what is the spec? I noticed there is not a cotter pin. Saw a couple videos on the tube no torque wrench used but I don't always trust the tube.....Thanks!


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## Skifftyz (Mar 9, 2019)

Is there a hole for a cotter pin and the pin is missing? Cant imagine they have done away with that.


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## Smackdaddy53 (Dec 31, 2012)

There may be a torque spec on some larger HP outboards but I’ve never used a torque wrench for a prop nut and never heard of anyone using one. I have installed props on a couple of these 115 ProXS outboards too. Just get the nut close to tight then turn until the hole lines up with the castle nut slot and install the cotter pin. The shaft is splined so there’s really no reason to need a torque spec. I like to use a cordless impact so you don’t need a block of wood to keep the prop from turning when you are tweaking the castle nut to get the hole to line up. I don’t recommend using the impact to run the nut tight, most people underestimate the force those things exert and tear shit up accidentally.


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## Mako 181 (May 1, 2020)

Sounds like he has been lucky to not lose the existing prop when going into reverse without a cotter pin.
Brand New Boat


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## Smackdaddy53 (Dec 31, 2012)

Mako 181 said:


> Sounds like he has been lucky to not lose the existing prop when going into reverse without a cotter pin.
> Brand New Boat


The splines will keep the prop from loosening the castle nut but the nut can definitely loosen up without a cotter pin…


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## rovster (Aug 21, 2018)

OK well before making an official accusation let me look again. I did look briefly and I did not notice a cotter pin which I found strange but let me double check. I may have missed it. That said on previous boats they were pretty obvious. Thanks for all the replies. I'll report back!


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## TravHale (May 17, 2019)

I have a Yamaha 200 SHO and it uses a standard prop nut and cotter pin. 

Quote from below DIY article from Mercury:

"Once the nut is hand tightened, you may now use a torque wrench to reach the specification of 55 foot-pounds of torque. If you don’t have a torque wrench, no need to worry, simply tighten down the nut with your socket. It will need to be pretty snug to avoid coming off when running your outboard."









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.


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## rovster (Aug 21, 2018)

No mention of a cotter pin in that article


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## TravHale (May 17, 2019)

rovster said:


> No mention of a cotter pin in that article


Nope. It probly uses a "locking" tab washer behind the nut.


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## Skifftyz (Mar 9, 2019)

TravHale said:


> Nope. It probly uses a "locking" tab washer behind the nut.


I watched a quick YT and the guy used 55 ft/lbs on the torque wrench and that locking washer you are talking about. That's my first time ever seeing one.

My 70 yam has a cotter pin and I've never used a torque wrench on it, but might start now if there's a torque spec.


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## Zika (Aug 6, 2015)

TravHale said:


> Nope. It probly uses a "locking" tab washer behind the nut.


My Mercury 60 used the tab washer instead of cotter pin. The new Yamaha F70 nut is locked in with a pin.


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## rovster (Aug 21, 2018)

There is definitely multiple layers under that nut. I did watch a youtube video on this particular engine and no mention of cotter pin either but there was like 4/5 layers of washers and stuff under the main prop nut.


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## Smackdaddy53 (Dec 31, 2012)

I went back through photos and found the first 115 ProXS I had in the shop and it has the washer with locking tabs. I didn’t swap props on this one but the next one I did.


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## millerrep (Apr 14, 2014)

Tab washer on every Merc I have owned. Tighten solid and line up the tab washer moving the nut in the tightening directing, then bend it in place. If the is pin hole use it.


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## m32825 (Jun 29, 2018)

The manual for my 20hp 4 stroke Merc has a torque spec, 8 ft-pounds, seems like the larger ones would as well.


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## Outearly (Oct 20, 2015)

I use a torque wrench to the suggested spec in the owner’s manual. Unlike someone like Smack who does it all of the time and has the required experience, I prefer to have the confidence that I got it right the few times I do it.


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