In search of cover nut tool

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lnick1975

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I replaced bearings and seals in my lower unit and am in need of a cover nut tool.
91-91947. Does anyone have advice or knowledge of installing this cover nut with a different more accessible, cheaper tool? I'm hesitant on spending $110 for one and am trying my darndest not to.
Or can anyone point me in a direction on where I can purchase a used one.

Thanks
Nick
 

Mercurylips

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lnick- I stopped at a Home Depot and picked up a "clean out" from the plumbing supply house. Then proceeded to use a pencil to mark, and a drill to grind out the proper tooth pattern. Finally sanded a bit and it fit into the cover nut. Drilled the cap that screws into the clean out with a spade bit so it fits over the prop shaft. I will try to post a decent picture for you soon. Mine is made for a 77 Merc 500 and as you know, size matters.
 

lnick1975

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Yes, I'd like to see a photo.
So were you able to torque it to the proper ft./lbs. with your tool?
That's one thing I'm definitely worried about.
 

Mercurylips

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Honestly didn't use a torque wrench on the plastic nor the metal rings I tightened. The plastic gets 1/2 of the amount a metal ring gets or about 100 FT. lbs. I also had some "old school" professional help when I put it and my metal ringed unit all back together. This called for a C-91-74241 Tool. Have no idea how my tool would mesh with a proper torque wrench I used water pump pliers. Sounds like you got yours off with out the tool. I got mine off and put mine together the first time without the tool and Then I needed to replace my shaft. So......The tool was created. I don't always trust my judgement but I do relax when my "retired" marine mechanic tells me to. He liked the heck out of my tool. What motor do you have.
 

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lnick1975

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I have a 1994 40hp. The nut definitely looks like yours.
I removed the old one by breaking it and chipping it away. So removal was really no problem.
It is supposed to be torqued to 100 ft/lbs, so i'm going to try and see if i can find a way to rig something to it to be sure its torqued properly.
Thanks for the photos, it really helps. I kinda thought about trying something like this so i guess i'll give it a go.
 

GA_Boater

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If the new cover nut is plastic, don't torque to 100 lbs or you will be buying another one. Only metal nuts are torqued that high, plastic is only about 50 lbs. Or a good grunt.

I made the same type of DIY tool as Lips.
 

Mercurylips

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If the new cover nut is plastic, don't torque to 100 lbs or you will be buying another one. Only metal nuts are torqued that high, plastic is only about 50 lbs. Or a good grunt.

I made the same type of DIY tool as Lips.

​GA-My Mercury Manual says 215 FT. lbs. (for the metal one). I'm sure the plastic was 100 as discussed on the forum.(may have been the "other" forum) It seemed to me that it was over the top but being a complete noob, I believe the manual but I trust my retired marine mechanic. If it breaks, it is nothing that money can't fix.:D
 

GA_Boater

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My motor calls for 110 ft lbs and the original is metal. The new one is plastic and I don't think it would take 110 lbs. Not an expensive part if it does break.

Ya pays yer money and take yer chances. :smile:
 

Mercurylips

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I have a 1994 40hp. The nut definitely looks like yours.
I removed the old one by breaking it and chipping it away. So removal was really no problem.
It is supposed to be torqued to 100 ft/lbs, so i'm going to try and see if i can find a way to rig something to it to be sure its torqued properly.
Thanks for the photos, it really helps. I kinda thought about trying something like this so i guess i'll give it a go.

​OK Nick. Let's trust what GA and my old pro said. Just get it nice and tight. I did some cross checking and the lower unit I have for a donor is a fit for yours. It had the plastic cover nut on it and my original has the metal. They are the same size and take the same size tool. The part numbers for the cover nut are the same as are the shaft and the bearing carrier . I have no idea why the tool part numbers would vary. This would be important if you order one. Take your nut with you when you shop. Mine just barely fit over the fitting and I think the clean out nut for the cap cost a tiny bit extra.
 

lnick1975

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I did notice the tool part numbers vary.
I think one is for an older tool which cannot be torqued properly and the new one can be torqued with a wrench.
I'm definitely going to make a tool this weekend and i'll torque it down to a grunt or two.
I'll give ya'll a heads up on how it goes.
Thanks for the advice
-Nick
 

qberttt

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Jul 24, 2023
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Honestly didn't use a torque wrench on the plastic nor the metal rings I tightened. The plastic gets 1/2 of the amount a metal ring gets or about 100 FT. lbs. I also had some "old school" professional help when I put it and my metal ringed unit all back together. This called for a C-91-74241 Tool. Have no idea how my tool would mesh with a proper torque wrench I used water pump pliers. Sounds like you got yours off with out the tool. I got mine off and put mine together the first time without the tool and Then I needed to replace my shaft. So......The tool was created. I don't always trust my judgement but I do relax when my "retired" marine mechanic tells me to. He liked the heck out of my tool. What motor do you have.
Ran into the same problem. I will have to make a tool and try to guesstimate torque as it won’t seal the bearing carrier against housing if not and then leaks. Love the tool idea.
 
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