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Lower unit distortion

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ShayneCastonguay

Contributing Member
So last season my 1982 50hp johnson outboard's lower unit cracked. I sent it to a friend who does aerospace welding to be welded, and it was. However, there is ever so slight weld distorition in the rear of the housing that does not allow the transmission casing to seat back all the way, my only real option is to modify the transmission casing to accomodate the slightly off-circle bearing seat, thoughts? I have access to full machining tools, mills, CNCs, lathes, etc.
 
No point risking damage to gears and shafts.----------Find a used housing as there are lots of them out there.------------Some welders do not understand that these are precision parts and may not function after welding.-----------Post a picture of the welded area.
 
I will post a picture tonight. About 300 degrees of the bearing housing remains intact, a small flat CNC'ed into the transmission case might make it fit past the distortion. The distortion is ONLY in the rear of the gear case, the front is intact.
 
Yes, a picture would sure help. I have no idea what you are calling a "transmission casing", or what we are giving advice on.
 
If the original gearcase was unmolested from the factory then no shimming changes will be required.-----------Just swap all the parts into the replacement case and you are done.
 
Just swap all the parts over and no shimming changes are needed.-----Note swap ALL the parts over and perhaps install a seal kit and new impeller.
 
I could not find a full seal kit, but i picked out all the important ones, along with a new impeller, last night. I will check the backlash on the gears, I'm not looking to put a new set of gears in
 
Let me rephrase, i bought all the seals that were dry or questionable, which was 90% of them. I'm sure the rebuild will go well, but i will let all of you know. Thank you!
 
Kim, a local dealer has asked me for used gearcases and I have supplied them.----Said " the custmer thanks you and we thank you "-----Same dealer has asked me to possibly do powerhead / gearcase rebuilds for them. --Their overhead is just too high and the young mechanics are not up to that kind of tedious / time consuming work.-And yes I do have the factory shimming tool for OMC gearcases.---------That tool never considers the reverse gear backlash because the OMC gearcases are precision made !!!!!!------40 years + experience does count !!
 
As racer stated as long as you keep the driveshaft and gears and shims together you can swap it to another case with no problems. You only shim the pinion height on a OMC as stated the housings are precision machined. Only time you need to check/reshim is if you replace driveshaft,upper bearing or gears. I also have the shim tool and gauges and the V-6 gearcase alignment check tool. You cannot do this with Merc units as you must shim forward and pinion height and backlash plus reverse!!!
Note: You cannot measure gearlash by feel and Youtube does not beat a manual!!!
 
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