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Old 10 May 2020, 07:24   #1
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Country: UK - England
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Oh No! Lower Unit Cracked

Bought a boat recently. Engine unchecked but the price was silly cheap.
Serviced and ran the outboard (Honda BF50) and got some gear oil in the bucket.
Turns out, I have a small crack on the lower unit just below the water intake. It's about 1 inch (on the outside.)
I don't really know what to do
Is it repairable? Can anyone recommend someone to weld? Am guessing I'd have to strip the whole unit which doesn't sound like much fun.
I've hunted for a lower unit but can't find anywhere in the UK. Any suggestions?
Any ideas how much this might cost to put right?
Location East Yorkshire
Thanks for any comments and help
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Old 10 May 2020, 08:19   #2
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Don't know if it would work, but I bought some stuff like plasticine and you just mix the two types together and it sets like a weld. I used it to fix a bracket and it set absolutely solid. Cheap as chips as well. You could force into crack and see what happens. Think Halfords sell something similar

Andy
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Old 10 May 2020, 08:28   #3
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Thanks for that. Not sure if this would work but might be worth a go. The crack is super fine so don't think would be able to fill it.... more cover?
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Old 10 May 2020, 08:37   #4
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You could try Ardoran Marine. They have some Honda gearboxes and look to be breaking BF40/50s so you never know. https://www.ardoran.co.uk/marina/out...tboard-engines

Because it's cracked, chances are it had water in the lower unit over winter and it froze. I've just been watching Dangar Marine videos or replacing propshaft seals. Looks like you would need to strip the gearbox down regardless as you'll cook any seals. The unit will need to be pressure tested afterwards. That probably means changing the driveshaft, propshaft and gear selector seals.

When they weld the lower unit they cut a V channel in the crack to get a proper contact weld.

Clyde Marine have a BF50 for sale too!
https://www.clyde-outboard-services....onda-bf50-lrtu
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Old 10 May 2020, 08:47   #5
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I had this issue on the gearcase of my DT200 quite a few years ago.

I first noticed it on holiday in Devon, so had to improvise.

I always have a few tools with me, so used what files, and actually a stanley knife, to carve out the crack into a 'V' shape and used a two part epoxy called Liquid metal to over fill the 'V' after I'd cleaned out the 'V' with acetone. I'm not sure you can still get it, but it was something I always made sure was in my toolbox whilst away camping and boating.
It's supposed to be as strong as Steel, and be able to take a thread with a Tap when dry.

It survived being used everyday for another week or so, then a few trips around the Solent. It was still OK when I sourced a used gearcase casting and rebuilt all my internals into the new casing.

I didn't have TIG welding gear myself at the time, so got a local company to weld up the old one to have as a spare after after I'd ground out the liquid metal.

The welding worked well, but was done on an empty casing that had been thoroughly cleaned and degreased. TIG welding it without the degreasing will draw the oil up into the weld pool and possibly cause issues as TIG welding has to be carried out very clean.

However, I was really surprised at how well the Liquid metal had adhered inside the 'V' I'd cut, and was convinced it would have lasted years.

You do need to ask why your casing has cracked though.
Mine had gone because corrosion around the threads of the main securing ring that hold all the gears etc in had expanded and 'blown' the tube part of the case apart as it expanded.
I'd suggest carefully whipping the ring out and cleaning it up before attempting to repair the crack.

Nasher.
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Old 10 May 2020, 09:05   #6
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Cheers Nasher, gives me hope. The small crack is on the main body. Can only assume it's had water in and frozen so may open it up a little and try your suggestion. I did wonder if this was possible but hearing your story gives me confidence this might do the trick. I did give the seals a bodge-it pressure test when i serviced it as the gear oil was well emulsified (before i spotted the crack) by suing a bike stand pump and spraying soapy water in with the prop off and no obvious bubbles so fingers crossed it might be OK.
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Old 10 May 2020, 09:28   #7
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You can still get Chemical Metal (made by Plastic Padding), although I'm not sure it's still the same ingredients? I used it on an old Yamaha outboard metal fuel tank years ago that had taken a dent at the top then corroded. Definately a temporary repair.

In fact I repaired a hole in my Honda mower cutting deck with it a few weeks ago after I'd patched it with fibreglass first.
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Old 10 May 2020, 09:32   #8
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JB weld is metal glue but I'm not sure it will fix this.
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Old 10 May 2020, 09:56   #9
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jb weld is good but you will have to get it really clean bare metal so it sticks properly .but it will work I had a porous diff on my ford ranger like a pepper pot I ground all the rust off drained the oil overnight then scrubbed it with thinners and blasted all the pock marks with aerosol carb cleaner to clean it then painted a coat of jb weld all over I ran it for a year after and it never leaked another drop of oil
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Old 10 May 2020, 12:07   #10
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I would strip the gearbox and weld the crack up itís the best you can do I think If you dig it out and fill it with stuff like jb weld it will leak again as the casting is structural and will move under the load in the gearbox thereís plenty of places opening up now put some pictures so I can get a look
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Old 10 May 2020, 12:46   #11
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https://ibb.co/cFm6njH
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Old 10 May 2020, 12:47   #12
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not sure how to post pic here.... have posted link for now. will try sort
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Old 10 May 2020, 12:52   #13
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Old 10 May 2020, 13:06   #14
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Thatís a stress crack that will need welded have the gears broken up and stressed the housing
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Old 10 May 2020, 13:08   #15
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Quote:
Originally Posted by breezeblock View Post
Thatís a stress crack that will need welded have the gears broken up and stressed the housing
Not that i know. Had the engine running a short while and in gear and seemed ok apart from the oil loss
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Old 10 May 2020, 13:10   #16
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I just had a 6" crack in the upper stabilizer fin of my BF40 welded. Worked fine. Sanded, primered and painted it with Honda Oyster Silver and clear coat.
looks like new. $60. You'll likely need to drain the lube out an maybe rinse w/solvent to get yours fixed due to the heat/oil proximity. Mine had the crack about 3/4" from the body but didn't need to do so.
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Old 18 May 2020, 15:23   #17
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I was recommended Belzona 1111 (super metal) and Devcon metal repair as they are both industrial epoxies which are supposed to be much better than (plastic padding) chemical metal which was described as a polyester body filler with metal dust fillers.
Didn't actually use either in the end so no experience myself.
Tony
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Old 25 May 2020, 03:32   #18
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May be worth trying Mark at
https://www.mjmarine.co.uk/contactus.html
He used to carry quite a few broken motors for spares but recently relocated and scrapped loads of his goodies so may not have as much ...
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