Mud Buddy Shaft Repair Advice Needed

Eric Patterson

Eric Patterson

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Staff member
I am helping Thomas rebuild the lower unit on his Mud Buddy Hyperdrive Sport. Water got into the lower unit causing the bearings to fail. Ordinarily water gets past the seals and his had that issue. But it also has a problem where the steel prop shaft housing is press fit into an aluminum socket (see black arrow in the picture below). The prop shaft housing, about an 1 1/8" in dia., is press fit in about 4" into an aluminum bearing housing that has worn to the point water seeps into the unit and destroys the bearing grease. I'm guessing it has worn several thousandths. I wish I could weld this joint but don't have the ability to weld aluminum to steel. So instead I'm thinking of pressing the parts apart and spreading one of several different compounds on the mating surfaces and pressing them back together. 5200 would be a good choice for this repair but I'm concerned the gap between the sleeve and socket is too narrow. Epoxy may work well but I'm concerned the different expansion of steel and aluminum will cause it to fail. I've looked into Loctite products but they make so many that all seem basically the same I don't know which one to use.

Any suggestions on how to fortify and seal this joint?

As a side note I'm really questioning Mud Buddy on their choice of aluminum for the bearing socket. Seems like steel would be superior. I don't think aluminum is up to the task. I wonder if other mud motor manufacturers have a better solution.






View attachment 35-HDR-Sport.jpg
 
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A 2-piece clamping collar holding an o-ring tight between it and the flare might provide a good seal. Before you try that, maybe a call to the manufacturer to see if they are aware of and have previously addressed this issue? Also, is there a zerk fitting for forcing grease into that coupling? Perhaps it needs to be greased frequently to remain watertight.
 
There is a zerk and a vent to keep it filled with grease. But when water finds an alternative path there's no keeping it out. Good idea on calling Mud Buddy. I'll do that.
 
Eric I'm no expert but i have had luck with engine heads aluminum head to cast block with a brown product my brother called "aviation sealant" its in a white can with a brush applicator at napa I believe permatex makes it under "form a gasket type" sealant. It may be worth a try. I think its like 7 bucks.
 
I have heard mud buddy customer service is nonexistant. That was a few years back when i was looking at mud motors though. You could try to get a machine shop make one out of steel then press it on and weld it. Or just get a new shaft assembly, less headaches than hoping a sealant works.


Good luck
 
Eric Patterson said:
I've looked into Loctitie products but they make so many that all seem basically the same I don't know which one to use.

Any suggestions on how to fortify and seal this joint?
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Eric,

I believe a Locktite product would be the best choice for sealing this joint. In the machine shop we used "Loctite # 620" for general purpose usage. The info on the bottle indicates it works on parts with up to a .015 gap.

I researched the current Locktite web site for possible other choices. "Locktite #648" would be a good alternate choice. #648 is rated "High" for retaining strength, #620 is rated "Mod - High" retaining strength.

I could not find a spec for "gap size" for either the 620 or 648 on the current site.

As to mechanically "fortifying" the joint; In spite of the upper brace coming off the prop shaft tube, it seems to me the tube must be flexing. Otherwise the bore for the tube should have no reason to enlarge and allow leakage. Possibly it was out of spec and bored oversize or tapered to begin with.

I am assuming the "skeg" and the upper brace coming from the prop shaft housing is providing structural support to the joint which is leaking. Is there any evidence the tube is flexing in spite of the bracing?

Might be possible to machine a "split" collar to be installed where the joint is to effectively increase the wall thickness of the aluminum socket. The split can be clocked (orientated) to allow for the skeg and still provide a clamping force to the aluminum. One half drilled and c-bored for the bolts and the other half tapped with threads.
 
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Hey Eric -

I may have the resources available to help. I have any number of people who can help you should you choose to go the adhesive route. From structurals to sealants; reactive polyurethanes and even hot melts, I believe I can get you in touch with an expert. Let me know. It?s not me by the way.

Mark
 
Appreciate the input guys. I contacted Mud Buddy and they recommended pressing it apart and using a thickened epoxy but couldn't recommend a specific one. Thomas posted the same question on the Facebook mud motor group and another guy who works at Mud Buddy messaged him saying DON'T press it apart. I have the guy's number and will call him later today. I wonder why his opinion of what to do it different from his coworkers. In the meantime I'm looking into sealants, like Locktite, to fix the problem. I plan to look into the ones Dave recommended and I would appreciate tapping into Mark's resources too. Of course before I get to that point I have to press it apart and there is very little of the end of the prop shaft housing exposed that I can press on (think of a tube with about a 1/32" wall thickness that has to be pressed out of a housing). That will be a challenge that maybe I can make a custom bushing that I can press the end of the housing with. Might have to take some pictures so you guys can see what I'm talking about.

Dave, you are a sharp cookie and I bet they miss your talents at your company. The upper brace has a couple bolts that attach it to a rib welded to the prop shaft housing and after you mentioned the brace I do recall it flexing when I pushed on the shaft. In fact I think the bolt holes have elongated thus allowing the flexing that is problematic. I am going to rebore the holes and use bigger bolts to eliminate the slop. Keen observation on your part.

Stay tuned....
 
Eric,
I suspect the coworker may be concerned about possible addictional damage that might occur trying to disassemble a joint that was not designed to be taken apart.

Heat may be your friend for disassembly. If the seals and bearings or at the least the seals can be removed first, then heat can be applied to the aluminum housing. Expanding it before the steel tube, thus loosening the hold.
If the joint is structurally secure a low viscosity sealant would wick into the gap providing the gap can be first cleaned with an appropriate solvent. This could be done without the need for disassembly. Acetone comes to mind and I can check when I get back home about a sealant to apply.
 
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Huntindave McCann said:
Eric,
I suspect the coworker may be concerned about possible addictional damage that might occur trying to disassemble a joint that was not designed to be taken apart.

Heat may be your friend for disassembly. If the seals and bearings or at the least the seals can be removed first, then heat can be applied to the aluminum housing. Expanding it before the steel tube, thus loosening the hold.
If the joint is structurally secure a low viscosity sealant would wick into the gap providing the gap can be first cleaned with an appropriate solvent. This could be done without the need for disassembly. Acetone comes to mind and I can check when I get back home about a sealant to apply.
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Dave

All bearings and seals have been removed. Nothing left but some paint on the outside that can be sacrificed by heat which you suggested and is a good idea. I'm interested in the low viscosity sealant idea. Wicking a sealant in there is something I hadn't even considered. Thanks.

Eric
 
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Eric Patterson said:
Dave

Wicking a sealant in there is something I hadn't even considered. Thanks.

Eric
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Eric,
Locktite # 603 from what I can find out, seems to be the thinnest (low viscosity) of the retaining compounds I researched. According to the data sheet it should be good for up to a .010 gap. This choice (#603) requires a 72 hour cure time minimum especially at maximum gap range. All the usage instructions call for it to be applied prior to assembly, however from personal experience, it will wick into other areas. (causing us some grief at times) Locktite recommends using their #7063 cleaner, prior to applying any of their retaining compounds. In the machine shop we always just used ink remover ( pure acetone).

If it were mine, based on what has been shared long distance, I would recommend a three prong attack.

(A) clean the joint with acetone and compressed air. Seal the joint with Locktite #603 retaining compound. Not only will this seal the joint it will also fill the gaps and help retain the steel tube in the aluminum bore.

(B) eliminate any slop in the bracing by up sizing the attachment holes if elongated. Possibly using shoulder bolts instead of regular bolts (which can measure as much as .008 under nominal size). Shoulder bolts are about .0015 under nominal and will allow less shifting within the hole. Recommend drilling slightly under finish size (64th under), then reaming the hole to size with a dedicated hand reamer. The length of the shoulder bolt should be just slightly less than the combined thickness of the parts. This way the bolt can still be tightened drawing the two pieces together and the unthreaded (full size) portion of the bolt will have maximum engagement of both pieces. One can purchase lengthening and /or shortening shims (thin specialty washers) to fine tune this down to the thousands, probably not needed in this application.

(C) once the Locktie #603 has fully cured, wipe away any excess from the face of the joint. (only that portion of the #603 contained within the joint will cure, see data sheet) I would then rough the outer surface of the tube and the aluminum housing at the joint and apply a JBweld product on the outside of the joint. A nice built up bead all around, will provide additional help to seal and strengthen the joint. I would definitely use the Marine version and have had real good personal experience with the bonding qualities of this product. I used it to attach brackets to an aluminum hull in leu of drilling or welding.

That's my story and I'm sticking to it. [ninja] Feel free to give me a call any early evening if you have questions.
 
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Another adhesive solution to explore is this west system 2 part epoxy. I use it to reseal leaking rivers and other marine applications. I would mix the adhesive and put a drop over the river. I would then beat with a heat gun and it would flow right into and around the river. Never had a leak after this fix. This is a highly recommended marine epoxy that is waterproof, somewhat flexible to deal with vibrations, and can get water thin when heated. View attachment 728DD55B-0DB9-45EB-B240-B7CCD09BA848.jpeg
 
Mark W said:
Another adhesive solution to explore is this west system 2 part epoxy. I use it to reseal leaking rivers and other marine applications. I would mix the adhesive and put a drop over the river. I would then beat with a heat gun and it would flow right into and around the river. Never had a leak after this fix. This is a highly recommended marine epoxy that is waterproof, somewhat flexible to deal with vibrations, and can get water thin when heated.
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I love the GFlex kits. I've used it on 2 boats now. I opened a kit this fall that has been sitting on the shelf for 8 years. Shelf life is exceptional. Obviously not the case as Eric is needing something but I do find that if your rivet goes through more than just the hull it won't seal good. For instance if the rivet goes through a keelson then through the floor it won't seal. Even if you follow the instructions and heat the epoxy. Water still penetrates around the rivet and through the hull. I have rivets I'll be pulling out this spring and replacing with leak proof blind rivets and 5200.
 
Mark W said:
So is it fixed and up and running? Enquiring minds want to know.

Mark
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Patience grasshopper,,,,,,,,,,,,, Eric said he was working on it just this last Saturday. Some of the recommended products require a 72 hour cure time before the item is put into service. Kids now days, all they want is instant gratification. [w00t]
 
Mark W said:
So is it fixed and up and running? Enquiring minds want to know.

Mark
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Threw my back out Friday at work moving cabling. Been laid up all weekend. Project put on hold until next weekend.
 
Eric Patterson said:
Mark W said:
So is it fixed and up and running? Enquiring minds want to know.

Mark
Click to expand...

Threw my back out Friday at work moving cabling. Been laid up all weekend. Project put on hold until next weekend.
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Ouch. Aren't you old enough to know no to that sort of stuff anymore? When I even have a dream of any physical activity I wake up sore.

Mark
 
Since my back is doing a little better and Thomas came home from school to work on the motor we went to the shop last night. Because the joint seemed fairly loose we decided to try and press it out so we could really clean things up and press it back together with Locktite 620 which Mud Buddy says they use and recommended in this repair. Pressing the steel prop shaft housing out of the aluminum socket proved quite easy. We heated things up with a couple torches and then pressed her right out. The press gauge never even hit 1000 pounds. With it apart we got a good look and saw no damage. In fact I could find no signs of Locktite, just some light rust and grease residue. I think they simply pressed it together without anything to seal or bond. We wire wheeled all the parts, hit it with some sandpaper to reveal and scuff fresh metal, and then cleaned it with acetone to remove any contaminants left behind. After buttering it up with the 620 we pressed it back together. That stuff was already doing it's job when we started pressing together, as evidenced by the gauge going over 10 tons. It went back together nicely. It will take 24 hours to cure but just based on how it looked after a few minutes I can't imagine it leaking or failing again. I think we got it right.

Next up is installation of shoulder bolts as Dave mentioned, and then 5200 around the joint for good measure, even though I don't think it is needed based on the tight fit. Finally we will reassemble the prop shaft bearings and seal. I hope it goes smoothly and expect it will.
 
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