Honda BF-45 Lower Unit Interior Corrosion

[SmithLakeHonda]

I am replacing the impeller or water pump on my Honda BF-45 and after finally breaking the bolts loose and getting to the pump I noticed that the inside of the lower unit is badly corroded. So much so that the transverse plates inside are rotted through in places. Will this be a big problem or can I spray some Zinc Chromate on the inside and try to get a few more years out of her. There is also one crack in one of the drive shaft housing thread holes.

Thanks

 

[ahicks]

I work on a lot of these 40-50 hp Hondas, but I've never seen one that bad. I'd be pretty concerned over what the inside of the engine looks like after seeing that.

That said, I say as long as the lower unit can supply water to the power head and keep water out of the lower unit lube, go ahead and run it into the ground. Keep an eye peeled on the engine oil dipstick . When you see milky oil or water droplets mixed with the engine oil, time to pull this engine from service. Judging by what the lower unit looks like this engine won't be worth fixing.

The upside is that when it does die, even though it's very likely going to be pretty used up, ALL of the parts are interchangeable with 40's and 50's built prior to 2004 or so. You might be able to find a parts motor on the cheap and build yourself a motor that will last quite a while using parts from this engine (e.g. carbs, ign. parts, starter, drive shaft, etc.) .

The older motors (especially those run in a salty environment) do have a pretty common issue. The bottom of the steering tubes are frequently rusting from the inside out, and haven't been made for a while now. Make sure your new motor has something to work with there! Best of luck! -Al

 

[SmithLakeHonda]

Thanks Al
I appreciate your input. The oil looks good and aside from needing a good carburetor cleaning, the motor was running good. It was however in need of a new water pump. (The impeller was ready to cause some major damage to the engine.) I did catch that thank goodness.

The corrosion is from sitting in fresh water for too long. I kept good magnesium anodes on it but apparently that was not enough.

Do you think cleaning and spraying the inside with Zinc Chromate will help to retard further corrosion, or do you have any other suggestions?

I like your idea about running her into the ground while looking for a donor/replacement 40/45/50 motor built prior to 2004. I will be keeping an eye out for a reasonable one on eBay.

 

[harringtondav]

Do you think cleaning and spraying the inside with Zinc Chromate will help to retard further corrosion, or do you have any other suggestions?

Cleaning and coating with anything is better than nothing, especially now that you have it wide open. I can't comment on the best treatment. I'd use a small nylon face brush on a 2" air angle grinder to clean up as much as possible. Then follow with an anticorrosion chemical (Zinc Chromate?), and then a good spritz of any aerosol paint you have laying around.

 

[SmithLakeHonda]

Thanks harringtondav

Sounds like a plan. I will do that. I have two cans of the Zinc Chromate so that should be enough to do inside and out and then follow up with Oyster Silver on the outside and a good heavy duty aerosol on the inside. [h=2][/h]

 

[ahicks]

Guys selling them on ebay think they are made of gold. MUCH better deals available by keeping a sharp eye on craigslist.

This one has a lower unit that's going to need some TLC and the trim is missing, but-
https://sarasota.craigslist.org/bpo/d/laurel-honda-40-horse-please-cylinder/7102005440.html

-OR maybe -

https://lakeland.craigslist.org/bpo/d/kissimmee-40hp-honda-outboard-motor/7107837173.html

A really common issue. You SHOULD pull that bearing carrier every other year or so, clean the corrosion and reassemble with a new seal. Otherwise corrosion builds up between the bearing carrier and the lower unit casting. If ignored, this is what happens-
https://staugustine.craigslist.org/bpo/d/saint-augustine-honda-50-lower-unit/7092280736.html

Believe it or not, if you have the piece that broke, these are routinely welded and can work for a long time afterward.

Last, if this is a fresh water engine, I wonder if you don't have some stray electricity running through the water that caused that damage. If that's the case, engine internals may not be affected at all. -Al

 

[SmithLakeHonda]

I have shore power but I keep it turned off. I have solar on the dock now. However, every once in a while in the past, I could feel a slight tingle when touching the aluminum ladder on the dock. It has not done that in years, but I did in the past. It wasn't my dock, but someone nearby must have had a problem. So I agree with your statement, "if this is a fresh water engine, I wonder if you don't have some stray electricity running through the water that caused that damage. If that's the case, engine internals may not be affected at all". Everything else looks good with the exception of the extension case and lower unit.

I will definitely keep an eye out on Craigslist. That one in Nokomis looks like a good deal, but I am not sure about freight though.

Again, thanks for all your help. [h=2][/h]

 

[MattFL]

I don't think turning off the shore power is enough, especially if your switch leaves the neutral and/or ground still connected. That could definitely contribute to electrolytic corrosion. If you leave any wires connected between your boat and the shore, your shore power needs to be galvanically isolated to prevent current flow. Here are some quick reads:

https://www.boatus.com/seaworthy/mag...ansformers.asp

https://en.wikipedia.org/wiki/Galvanic_isolation

A snippet from that first one:

"Isolation transformers also prevent galvanic corrosion that can occur between boats in a marina that share a common ground through the AC shorepower. This connection can cause neighboring boats to damage or destroy each other's less noble underwater fittings, like aluminum outdrives."

 

[SmithLakeHonda]

Thanks MattFl,

I am just now seeing this and this is excellent information. I really do appreciate the links.

I actually replaced the GFI yesterday and turned on the power to charge my batteries and while I was at it, I dropped a voltmeter into the water to see what the current would be with the power on and with the power off. (One lead in the water and one lead touching the steel dock.)

The results were 0.258 volts with the power disconnected and 0.40 with the power on. I checked a little later with the power on and the result was 0.250. I believe that I read somewhere that water has a low electrical charge anyway so this is probably normal.

My ultimate goal is to get away from AC current altogether on the dock. I currently have a solar powered boatlift and I am going to install a solar panel on the roof to provide LED lighting and to charge my boat batteries.
I guess I need to review/or start a thread in the electrical forum for guidance.

Thanks again