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Old 03-02-2010, 01:28 PM
Lusox Lusox is offline
Join Date: Jan 2007
Location: Johnsonville, Wisconsin, US of A.
Posts: 220
Default Repair of a small hole in a lower unit

Neighbor has a Merc. outbard - '80's - that has a small hole poked in the lower unit and I'd like to repair it for him. I've got TIG welder but know that welding cast aluminum is no fun (also concered that the cast alum. has soaked in lube to the point the it wouldn't work anyway).
Have also considered J-B welding an aluminum patch on it.
Any thoughts on this?

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Old 03-02-2010, 04:40 PM
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ffishman ffishman is online now
Join Date: Sep 2004
Location: Schaumburg, ILL, USA.
Posts: 7,674

I know there are places that do it, but I don't know how they do it.
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Old 03-02-2010, 05:56 PM
staylor staylor is offline
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Location: North Tonawanda, NY, USA.
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Default Need more info

Like how big the hole is and exactly where on the lower unit it's located.
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Old 03-02-2010, 07:54 PM
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propmann propmann is online now
Join Date: Feb 2008
Location: Brainerd, MN.
Posts: 1,518

Should be no problem welding it up, we done quite a few of them. Depending where the hole is you may need to pull the guts out. Clean it the best you can, take your tig torch and try melting edges this will bring up more oil and dirt grind it again try melting it again, may have to do that a couple of times before it will start welding. Good luck
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Old 03-03-2010, 10:55 PM
REW REW is offline
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Join Date: Nov 1999
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Posts: 30,858

Be careful.
Why is there a hole in the lower unit?

If the lower unit hit something, did it do something to the lower unit beside knock a hole in the case?

Also, remember, the lower unit has to be both pressure proof, as well as vacuum proof.

The best way to weld up the lower unit, is to
a. remove the lower unit.
b. remove the lower case internals.
c. weld up the lower unit.
d. replace the lower case internals.
e. pressure test and vacuum test the lower unit for 24 hours each.
f. replace the lower unit - add oil and enjoy.

The key thing is to be sure that what ever hit the lower unit - did NOT tweak the case which will cause the bearings and internal shaft to get misaligned. If the shaft gets misaligned, the shaft will eventually come through the side of the case and will seize up and leave the boater stranded.

If I had very much suspicion of a very hard hit on a lower unit, I wouldn't repair the case. I would find a different case and or lower unit and drop it back on the motor.

Take care
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Old 03-04-2010, 06:27 AM
jokerjim jokerjim is offline
Join Date: Nov 2007
Location: Deerfield, Illinois
Posts: 460
Default Hole

Depending how big the hole is, could you drill and tap threads in the hole and put in the proper size plug( with lock tight) ? For cosmetic purposes you could grind down the plug and cover with bondo, sand and paint.
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Old 03-04-2010, 08:59 AM
Lusox Lusox is offline
Join Date: Jan 2007
Location: Johnsonville, Wisconsin, US of A.
Posts: 220
Default Thanks

I haven't seen the "hole" yet, I'll try to get a look at it today. Sounds like the welding is doable ( if the unit is not entirely tweaked).

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Old 03-04-2010, 12:01 PM
bcmss396 bcmss396 is offline
Join Date: Nov 2009
Location: Colgate, WI
Posts: 277
Default Lower Unit Repair

Years ago we used a product called Marinetex to patch a giant (silver dollar) size hole in the front of a lower unit after it smashed ainto a rock.

The lower unit lasted the remainder of the trip (5-7 days) and finally gave up the ghost. We still got to enjoy our trip.

That product on a smaller scale with no serious damage to the interior supports and workings would probably work for you.

Good Luck.

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