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

Wood Zeppelin

I have a crack in the housing around the propeller shaft.

The first question is: Does anyone know how/why this happens?

The second question, where do I find an affordable replacement (used?).

thataway · Posted: Sat Oct 28, 2023 1:09 pm Post subject:

Wood Zeppelin · Posted: Sat Oct 28, 2023 11:26 pm Post subject:

Thanks!

Turns out it is not leaking any gear oil, nor is the gear oil taking on water!

I'll try to take a pic in the next few days and post it,,

Wood Zeppelin · Posted: Sat Oct 28, 2023 11:28 pm Post subject:

Wood Zeppelin · Posted: Sat Oct 28, 2023 11:32 pm Post subject:

Could it be welded?

What about JB Weld and a SS hose clamp to keep it from propagating in the meantime?

thataway · Posted: Sun Oct 29, 2023 2:52 am Post subject:

Hunkydory · Posted: Sun Oct 29, 2023 12:41 pm Post subject:

James, approximately 14 years ago in about 2009, I had a damaged lower unit housing on a 1999 Honda 40 hp from the process of replacing the seal. A new housing at that time was $600 & if available, I imagine much more now. Lots of those motors made, so probably E Bay or the like, the best bet. That motor with new gear housing was still going strong, when the motor was replaced by new Honda 60’s in 2019.

As far as the JB Weld, it is amazing, so a possible option, but it would be a gamble, which I did take on a 1984 Ford F250 with the 6.9 L diesel engine in 1991. A 2.5 inch crack formed out of the hole in the block, where the cold weather block heater was inserted. The truck at that time was 7 years old & the block replacement or removal to have special welding done, cost prohibiting for us at that time, so I ground out about half way down through the crack it’s length & drilled a small hole in the end of the crack, then inserted a metal screw in the hole coated with JB Weld to stop the crack from further growth. I then, filled the ground out part of the crack with JB weld. Even under the coolant pressure & the crack originating in a pressure point from the inserted block heater, the JB Weld prevented leaking for about three years. I ran that truck for another 20 years & 150,000 + miles by replacing the JB Weld at about three year intervals. If it weren’t for where the crack originated, the JB Weld may not have had to be replaced.

Jay

T.R. Bauer · Posted: Sun Oct 29, 2023 4:03 pm Post subject:

I would replace the whole assembly. It's not cheap....but you get to start out new. As far as what happened to yours? So many things could have happened....but if you haven't hit anything with it, it would not be the first one that corroded where the packing nut that threads into case (the one you remove to change the seal) caused the crack to form. The nut, the case, and the shaft all have different metallurgic properties and interact with one another. After a long enough time, well.....the threaded nut going into the case sort of expands and then you get a crack in that spot. It will eventually fail catastrophically one day.....It really isn't the best design in my opinion. I'm sorry it's your turn to deal with it. BTW....they can be TIG welded in the right hands, but everything must be disassembled...expensive.

Wood Zeppelin · Posted: Tue Oct 31, 2023 1:38 pm Post subject:

Thanks for the thoughtful responses guys!

It looks like I have a few options:

https://www.ebay.com/b/Complete-Outboard-Lower-Units/177671?Brand=Honda

thataway · Posted: Tue Oct 31, 2023 2:18 pm Post subject:

Wood Zeppelin · Posted: Tue Nov 14, 2023 2:44 am Post subject: Used, or swap parts in

Looks like I have two options. I'm wondering what you guys think is best:

(1) I can get a used lower unit, but I take some risk not knowing the condition of the gears and prop shaft runout, etc.

(2) I can get NOS housing, and swap in the parts from my old one.

Question: Option 2 seems like a safer bet. But I have never done this job before. It is super hard and complex? Are special tools and techniques required?

thataway · Posted: Tue Nov 14, 2023 3:58 am Post subject:

There is a special wrench:" Lock Nut Wrench, 62 mm, 07LPA-ZV30100". this may have been superseded by a similar number but the last is ZV31010 They cost from $200 to one one $250.

Upon further reading it appears that many of these cracks stem from a design flaw and corrosion of the unit and carrier nut. The carrier nut should be removed once a year and threads greased, then put back in place.

The problem with welding is that thee is a good that the threads in the gear case That the carrier nut threads into will be damaged. In hat case you would have to find a machine shop to repair the threads....may be easier and cheaper to buy a new one.

Wood Zeppelin · Posted: Tue Nov 14, 2023 12:00 pm Post subject:

thanks!

Yes, I am seeing on the internet that it is a known problem. I wonder if my 1998 BF40A is still covered by Honda?

Also, I have a 2006 Honda 50hp and 9.9hp. Does anyone know if this design flaw still existed in 2006?

thataway · Posted: Tue Nov 14, 2023 1:40 pm Post subject:

Pretty unlikely that s 1998 motor would be covered by anything from Honda. On the more recent motor, I would pull the carrier nut and check for corrosion. I have a Seloc Manual (2002 to 2008) for Honda (2 to 225 hp). It is not as detailed as the full shop manual (which I had for the 150 series). Rebuilding the gear case is above my pay grade. Part of that is that I don't have the specialized tools, which are necessary.

When the assembly is out, then both check for corrosion and the threads, lightly grease before reassembly.

My impression is that Honda has more corrosion issues that the majority of outboards. (Based on owning both a number of Hondas, OMC, Suzuki and Yamaha outboards.). There are members on the forum who do rebuild some of these motors and hopefully they will weigh in.

Hunkydory · Posted: Tue Nov 14, 2023 2:09 pm Post subject:

No cracks around that area on my Honda 40’s with about a half of their 2400 hours usage in salt water, but when I needed to have the lower unit seals replaced on my then 1999 Honda 40’s, I found like Bob the price of the special tool to be $200 +, so I made the rare choice for me of towing it to a dealer 150 miles away to have the work done at about the same price for the special tool. They didn’t have any problem with the one lock nut, but the other was so corroded, the case was ruined getting the nut off. I chose to have a new case at the price of $600 at that time & they changed out the internals at no charge, which surprised me as if I had bought the special tool & did the job, no doubt, I too would have ruined the case, so in this instance, glad I chose to have the job done by a Honda Dealership.

At that time there was no mention of this being a known problem, but any of those bolts & nuts that spent a good percentage of their time in salt water were known to corrode, so I would grease when ever I took them apart. On my Honda 2019 Honda 60’s, when taking off the lower units to replace the water pumps, I noticed the bolts all had grease or anti seize on them from the factory. It wouldn’t surprise me to find the locking nut does now too.

My Honda 60’s have a lot of anodes to replace & I'm doing that with replacement perhaps to soon other than to late.