Got off the marsh today and found grease leaking from the top of the Prop Shaft Casing (Actual Name - Drive Sub-Assembly). It is just forward of the welded top brace. I wiped off the grease to find a hairline crack. I have not abused the motor, a Mud Buddy HD Sport.

1. What would cause this?
2. Is it fatal?
3. Can it be repaired - Temporarily or Permanently
4. Can I use it in the interim? At what risk?

I would appreciate your comments. Know many of you do not think much of Mud Buddy, but right now it is what it is, and I've got to figure out the fix.

Thanks in advance for your productive comments and suggestions.

Charlieboy

Seems like mb has had a few of these out there. Ive seen quite a few complaints of the cracks in the shaft housing on here. Maybe stop drill the crack on each end and weld it up. I dont know how longthat would last. Might need to search for a new housing.

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So I've got several sources that are pretty confident I can weld. Gonna try that as a temp fix, get through the season and then replace... Several people are suggesting the crack is likely the result of a prop that is out of balance, causing excess vibration.

Couple more questions...

1. Can I do the weld, you think, without disassembling?
2. Do you buy the idea the cause could be vibration from an out of balance prop?
3. Is there an easy way to tell if your prop is out of balance?

Thanks again in advance for your constructive input.

I'd disassemble or when you go to weld on it the high temp is going to ruin your seals and that will just be another problem.

Do what I did.. Weld it up and grind the evidence.. never happened..

Its a design flaw....call mb and tell them what you need....
sent from the former Republic of Texas.

what year is it and where are you located?
this isnt a new issue barnes is on his 3rd lu i believe and i think he may barely be over 100 hrs and he takes care of his shit, guess they just dont wanna fix the problem

My buddy had the same thing happen to his 10 yr old GD 35 SD last month. Coco sent him a bracket that he had welded on. It's working so far. That bracket would probably work on your MB.

They probably should hire some engineers!

Without seeing the crack fracture surfaces, a person really couldn't say what caused it. If somebody was able to get one of these and cut it to expose both sides of the fracture, it would probably be possible to tell what caused the crack...whether it was fatigue related, stress related or if there may have been some other factor. Especially if you can get it right after it happened.

Just thinking out loud from a metal head standpoint....I would guess one of two or combo of both may cause this problem:

1. Fatigue from out of balanced prop. The out of balance causes a vibration along an unsupported length of housing and it fatigues.

2. Grease gets low or hot in the housing could create a thermal fatigue. Housing gets hot while running, then is cooled instantly when you stop. This constant cycle of hot/cold would create a thermal fatigue.

With the second theory, the housing could also be getting hot, trying to expand (grow in length) and there is no place to go because of the skeg/cavitation plate design keeping it from expanding. In other words, the skeg/cav plate are not getting hot and expanding. This type of failure would likely occur adjacent those attachments, though....near a "stress riser" in metallurgical terms.

Just my $0.02 for what it's worth. I know it didn't fix your problem. But, hopefully, MB will make it right for you since this seems to be a recurring issue.






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They probably should hire some engineers!

Without seeing the crack fracture surfaces, a person really couldn't say what caused it. If somebody was able to get one of these and cut it to expose both sides of the fracture, it would probably be possible to tell what caused the crack...whether it was fatigue related, stress related or if there may have been some other factor. Especially if you can get it right after it happened.

Just thinking out loud from a metal head standpoint....I would guess one of two or combo of both may cause this problem:

1. Fatigue from out of balanced prop. The out of balance causes a vibration along an unsupported length of housing and it fatigues.

2. Grease gets low or hot in the housing could create a thermal fatigue. Housing gets hot while running, then is cooled instantly when you stop. This constant cycle of hot/cold would create a thermal fatigue.

With the second theory, the housing could also be getting hot, trying to expand (grow in length) and there is no place to go because of the skeg/cavitation plate design keeping it from expanding. In other words, the skeg/cav plate are not getting hot and expanding. This type of failure would likely occur adjacent those attachments, though....near a "stress riser" in metallurgical terms.

Just my $0.02 for what it's worth. I know it didn't fix your problem. But, hopefully, MB will make it right for you since this seems to be a recurring issue.






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I appreciate the insights, and advice. I AM the kind of guy who will push them to give me some satisfaction, and I'll see how they respond. So far, they have been responsive with calls and emails, but I have not pushed them for anything of consequences. I will keep you posted.

To answer some questions... It is a 2007. NO record of hours on this one. Motor in EFI 27hp Kawasaki with water cool. I bought used in summer 2012. I am in Wisconsin, and run it in soft mud marsh. I have not been that hard on it, in my view. The prop has some nicks in it, but nothing serious, and least in my humble opinion.

Got it welded, without disassembly, to make it through the rest of the season. Will assess then, and after some serious conversation with MB, about what to do long term. The welder is confident he got a good weld, did not use a drill stop.

A question remains... Is there a relatively simple way for a novice to tell if the prop is out of balance?

who says I ain't already done that? or that I'd want to? She's too damn skinny.

might crack her like a MB lower unit haha

Hey Paul, Mark is on his second or third as well. Its surely a design flaw!

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no kidding... I will PM him and see if he has gotten any satisfaction. thanks for the heads up