Cracked! - Need a lower unit for Honda BF40 (1997)

Wood Zeppelin · Posted: Wed Nov 15, 2023 11:22 pm Post subject:

How do I post photos here?

thataway · Posted: Thu Nov 16, 2023 12:01 pm Post subject:

Wood Zeppelin · Posted: Sat Nov 18, 2023 10:40 pm Post subject:

Thanks Bob

Wood Zeppelin · Posted: Sat Nov 18, 2023 10:48 pm Post subject:

So the crack has not made it to the gearcase oil cavity. I could:
- Drill a hole at the end of the crack to prevent further propagation...
- Grind the crack open a bit to expose more surface area for bonding
- JB weld the crack
- Then I'd like to put some kind of Stainless Steel bank around the housing, just before the flange at the end near the propeller.

Thoughts on this approach?

Wood Zeppelin · Posted: Sat Nov 18, 2023 10:50 pm Post subject:

Freshwater vs Saltwater question..

I also plan to only run it in Freshwater (such as Lake Powell) for the foreseeable future. (it used to spend 2-3 weeks per year in Puget Sound).. Is it safe to say the "corrosion-expansion" that caused the crack will halt as long as it's not exposed to saltwater anymore?

T.R. Bauer · Posted: Sat Nov 18, 2023 11:25 pm Post subject:

srbaum · Posted: Sun Nov 19, 2023 9:54 am Post subject:

WZ,
I repair about 50 outboards a year and have repaired near a thousand in my lifetime. I would not waste my time with repairing it. I would buy a used one in almost 90% of the cases. I have had good luck with buying used ones from reputable shops that sell used lower units. Most of these reputable shops will replan a defective unit.

thataway · Posted: Sun Nov 19, 2023 11:53 am Post subject:

I took the liberty of posting two of your photos in larger format, to see the amount of corrosion detail. (if you copy the first image you see on your photo album, they will be small--probably because of a small file. If you double click then it will come up this size:

After studying these, I agree 100% with srbaum who has extensive experience with these motors. Also agree with T.R. Bauer that we really don't know what the future of the corrosion and extending of the crack

Any of the your suggested remedies will not really do a lot in the long run. These photos also bring up the condition of the water passages in this motor. I would pull the thermostat and examine what you can easily see. I would also suggest running the motor in a tank which has salt away added for at least getting up to temperature, and then running for 15 more minutes.

I have dealt with overheating issues on Powell several times, and these were usually when we had gone back into canyons or to the navigable head of the San Juan River, where there was a lot of debris. However we have had it happen in both Powell and other fresh water venues, where a fairly small debris field or grass will plug up the water intake. Stopping and reversing the motor cleared the debris off the lower unit.

Replace the lower unit.

T.R. Bauer · Posted: Mon Nov 20, 2023 3:03 pm Post subject:

Hmmm....seen that lots of times before on honda outboards. I had one like that too. It's time for a new lower unit if you like going out on the water and not worrying about it. BTW, no way that crack stays static. If somebody showed up and asked me to TIG weld that? I'd say you're throwing your money away. Lower units are not free, but as far as boat money goes, they aren't that much either.

Wood Zeppelin · Posted: Thu Nov 23, 2023 2:39 pm Post subject:

Wood Zeppelin · Posted: Thu Nov 23, 2023 2:41 pm Post subject:

Wood Zeppelin · Posted: Thu Nov 23, 2023 2:44 pm Post subject:

Wood Zeppelin · Posted: Thu Nov 23, 2023 2:49 pm Post subject:

OK, next big question...

Did they improve on this design in later models that I can swap in and bolt directly to the top half of my motor?

I talked to a guy at shop that services Honda's, and he kept referring to the "two bolts" that hold in this parts of the gear case in place. When I'd mention one big internally threaded nut, he'd go back to talking about the "two regular bolts". I know some other motors have this design. Do later model BF40/50's have this improved design that I could use?

thataway · Posted: Thu Nov 23, 2023 3:01 pm Post subject:

You can get a parts diagram for your motor by google. That will tell about the bolts.

You will most likely have to go to salvage yards or E bay to find the "used but in good shape" lower unit. You should always do a run out dial caliper on one of these to assure that the prop shaft is not damaged. If it is out of true, send it back.

srbaum · Posted: Thu Nov 23, 2023 7:03 pm Post subject:

WZ,
Give a call to Atlantic Marine, they are wonderful people and truly Honda outboard experts. They specialize in selling and installing Honda's to the military, as well as to commercial and recreational boaters. They are also the go-to for rebuilt or new lower units.
www.atlanticmarineva.com