Hairline lower unit crack.

[DrummermanBob]

I just noticed an inch long hair line crack in bottom half of lower gear case housing. It is hardly noticeable unless you run a finger nail over it but I could see small amount of gear oil leaking out of this crack. Can I use JB Weld on this if prepped properly?

[crosbyman]

you may be able to seal the GC from the inside with the application of an oil resistant product …  (JB weld ??)

I have a nice  CD 5.5hp with a simliar problem but can’t feel the crack but it does leak…  from somewhere !

when I have time i’ll mix in some UV dye  in the GC oil  and  flash a UV lamp to  see where it leaks. … probably will have to split the GC  lower half to reseal it from the inside…after a good   wash & rinse with  lacquer thinner   followed up  with  something…to seal it

maybe crazy glue can seep in the crack and  seal it good ?

 

suggestions accepted 🙂

 

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[Mumbles]

Depending on where the crack is, there might be a lot of stress on it which could lead to a total failure down the road. Probably best to replace the part or have it welded.

[DrummermanBob]

Yeah, you’re probably right. Is it true that the two halves of a Johnson FD12 lower unit were matched at the factory and interchanging is not possible?

[fleetwin]

It will be hard to patch that crack from the outside because of the gear oil residue that is constantly weeping through it.   And yes, the upper gearcase and skeg are matched pieces from the factory and not meant to be interchanged, but plenty of people have done it and gotten away with it.  A gamble for sure, I guess I would test it out by assembling the unit “dry” with no sealer to make sure things fit and rotated properly, before going through all the effort of sealing it up..

I would follow Mumbles’ advice if you have access to a talented tech who is good at welding aluminum..  Just make sure the weld bead does not interfere with the rotating gears, seems unlikely but anything is possible.

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DrummermanBob

[crosbyman]

see some utubes on GC solder jobs…

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[crosbyman]

anybody ever tried this stuff to seal airline cracks  in GC  ??

https://www.amazon.ca/Bars-Leaks-1040-Repair-Concentrate/dp/B00754T6TK/ref=asc_df_B00754T6TK/?tag=googleshopc0c-20&linkCode=df0&hvadid=292962948623&hvpos=&hvnetw=g&hvrand=291688734790867626&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9000433&hvtargid=pla-568295712142&th=1

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[DrummermanBob]

Thanks

[DrummermanBob]

Thanks!!

[joecb]

Much to consider in your decision as mentioned above. Possible structural issues aside, sealing that crack will be difficult because of the oil contamination. There is a Locktite product that is designed to wick into minute cracks. It’s the Green wicking products called “sleeve locker” or “thread locker”. Having used these products, I’m sure that they would wick into the crack and seal it… problem is the oil contamination. How to clean the crack?? , solvent maybe or bake it ??

Joe B

[Author]

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