Crack repair on lower unit

Muddlerman

Cadet
Joined
Jan 15, 2006
Messages
17
I have a 61 Johnson 40hp. I noticed a 3/4" crack on the lower unit above the prop on the trailing edge.<br /> Are there any products, expoxy, that I can use to fill this. It seams small but I noticed a bit of "milk" when I drained the oil. This may be the source.<br /> Thanks<br /> Muddlerman
 

Magnum1500

Seaman Apprentice
Joined
Jan 9, 2006
Messages
33
Re: Crack repair on lower unit

Try a ring around at the outboard wreckers to see if they have a spare gearbox before you attempt the repair, it maybe easier to buy a good working gearbox, change its oil and bolt it on to your mid section. If you can't find a spare then repair as follows:<br /><br />1) drain the oil<br /><br />2) drill a small hole at each end of the crack say 5/16" or a little less. This will stop the crack from growing any further.<br /><br />3) grind a V-prep into the crack and degrease the area as best as you can with alcohol.<br /><br />4) neatly fill the v-prep with "Devcon" epoxy filler.<br /><br />5) carefully sand back, but leave the repaired surface slightly proud to increase the strength surface, prime and paint.<br /><br />6) don't forget to refill the gearbox with oil when you're done.<br /><br />Alternatively you could weld, but on a 50 year old casting with oil reside present it might not be very succesful.<br /><br />Good luck.<br /><br />alterantiv
 

Coleman1977

Cadet
Joined
Feb 11, 2006
Messages
16
Re: Crack repair on lower unit

Ouch. I have been there before and here is what I did as replacing lower units can be quite costly and I was looking for an inexpensive fix:<br /><br />-Drain the lower unit and let it drip for a day or two to remove as much oil as possible.<br /><br />-Using a drill just larger than the crack, drill holes at each end of the crack (this keeps the crack from running further)<br /><br />-Using a small grinder (Dremel) tool, clean out the crack as best as possible.<br /><br />-Sand the area just ouside and around the crack with course sand paper to remove paint to bare metal<br /><br />-Clean entire area with mineral spirits or degreaser being sure to get some into crack. make sure to keep the unit on the side with crack up so no oil from inside drips back into crack<br /><br />-Use JB Weld to cover the crack entirely, being sure to get some down into the crack and into the drilled holes. Let set-up then re-apply several coats, letting each set-up and with each coat a little larger/wider than the previous coat. <br /><br />-Sand down (Dremel tool again works well) to remove any "high spots" and to obtain a uniform appearance as best as possible<br /><br />-Repaint<br /><br />Once this is complete, be sure to refill with oil and check the lower unit to be sure no seals are leaking and that the cold weld worked efficiently.<br /><br />I used this process on a 3" crack that I accidentally got and the fix held for 3 years until I eventually sold the boat. I used the boat almost every weekend, so I am a believer in this method. Take special care to follow all the details above and you should end up with a like new lower unit, less the minor scar's appearance.<br /><br />I tried this as I could not afford a new lower unit and didn't have time to find a capable/cheap welder (the fish were biting)but was surprised at the results.<br /><br />Good luck!<br /><br />Coleman
 

OBJ

Supreme Mariner
Joined
Dec 27, 2002
Messages
10,161
Re: Crack repair on lower unit

If it's not directly on the gear case, look elsewhere for the cause of the "milk". <br /><br />Just to clarify, your description puts it above the prop on the anti-cavitation plate. If so, clean the area good removing all paint and fill it in with epoxy if you like. Feather out and paint.
 

Coleman1977

Cadet
Joined
Feb 11, 2006
Messages
16
Re: Crack repair on lower unit

Magnum - good advice! You must have hit send a nano-second before me!!<br /><br />Coleman
 

Muddlerman

Cadet
Joined
Jan 15, 2006
Messages
17
Re: Crack repair on lower unit

Thanks folks,<br />Magnum & Coleman, It goes to show that great minds think alike. <br /> How deep should I drill? <br />The crack is halfway between the prop & the cavitation plate, 1/4" in from trailing edge.<br />It may be solid there, but I still don't want to take any chances.
 

OBJ

Supreme Mariner
Joined
Dec 27, 2002
Messages
10,161
Re: Crack repair on lower unit

Quick way to find out Muddler....put a pressure test on it and submerge it in a garbage can full of water. It'll show you right now if the crack is cause for alarm and any other leaky seals you might have.
 

Magnum1500

Seaman Apprentice
Joined
Jan 9, 2006
Messages
33
Re: Crack repair on lower unit

sorry made a mistake there (5/16")?. I meant 3/16" I had a figure of 5mm in my head. I come from the metric system.<br /><br />You may want to drill the hole at each end of the crack with 1/8" and then countersink it with a bigger drill like a 3/16", as the epoxy will nicely fill the countersunk areas at each end of the v-prep you grind.
 

Coleman1977

Cadet
Joined
Feb 11, 2006
Messages
16
Re: Crack repair on lower unit

And if it is a source of leaks, do drill all the way through the crack/wall of the unit. Otherwise, the crack can still run, leading to eventual failure.<br /><br />Coleman
 

Muddlerman

Cadet
Joined
Jan 15, 2006
Messages
17
Re: Crack repair on lower unit

Thanks for the advise. I hope to see some open water here in Maine in a couple of weeks.<br /> Muddlerman
 

floatingwoody2006

Chief Petty Officer
Joined
Feb 2, 2006
Messages
500
Re: Crack repair on lower unit

Hey muddler.. I live right down the road in gray.. If your off the Range ponds up there your in prime fishing territory. SOme of my favorite places to go.10hp and under at lower range though. As soon as Crytal lake thaws out down here.. I will test my new to me rig..Hope to see ya out there..
 

hustler70

Cadet
Joined
Mar 17, 2006
Messages
6
Re: Crack repair on lower unit

drain the oil, sand out the crack with a dremel then marine text it
 

Paul Moir

Admiral
Joined
Nov 5, 2002
Messages
6,847
Re: Crack repair on lower unit

That passage that's cracked is a drain for the bottom of the exhaust cavity in the lower unit, via a weeping hole on the starboard side of the gearcase. If you fill it (which will work fine) the cavity will no longer self drain. It probably clogged up and water froze in there.<br /><br />What this means is you'll have to take a little precaution if you store it somewhere freezing in the winter. Let the outboard stand upright for a while, then tilt it as close to horizontal as you can and let the puddle drain out. Then back to vertical.<br /><br />I've got a couple L/Us like that. None of them cracked into the gearcase causing water infiltration or any other problems. Ones even got the whole side busted off.
 
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