Fresh water corrosion and anode choices…

[Crispin]

Our 2004 DF140 has corrosion attacking the lower unit. We just recently discovered this hole with water draining out when the engine is tilted. We’re on Lake George in NY and the water while being drinking quality may be slightly acidic. Edit- just read ph ranges between 7.5-8.
I recently read about different alloys for anodes and would like to know if something is better for this lake water over salt water. We have never changed the anodes in 20 years so maybe it’s just that. Do they develop an oxide coating that stops them from working?
Also, can anyone speak to what’s behind this hole? If I can stop the bleeding with new anodes, could this be a JB Weld fix?
Thanks in advance for any help, C

 

[Lou C]

That’s more than slightly acidic water! Was it left in the water in a hot marina? That’s a lot worse than my Cobra outdrive looks after being moored in salt water for 20 seasons!
And you need to use the correct anodes for freshwater which is magnesium not alu or zinc. I use zinc in salt water & change every season they are not even 1/4 deteriorated but I want the most protection I can get

 

[racerone]

A product called ----lumiweld-----can repair that.

 

[Crispin]

A product called ----lumiweld-----can repair that.

So is that a water/exhaust passage and not connected to the inner gear case?

 

[racerone]

Not connected to the gearcase oil cavity.-----If it was , the gearcase would have come to a dynamic halt long ago.

 

[garbageguy]

... ph ranges between 7.5-8...

sounds like your water (in the slip?) is basic

salt water is generally more conductive, but there is likely stray current in your slip, if you're in one
I would replace the anodes - you could go with a "softer" metal, see what a reputable local uses

 

[racerone]

Tilt the outboard up when in the marina.

 

[Crispin]

Thank you and I figured that but also wondering how terminal this for this engine and lower unit? I feel kind of dumb for not reacting sooner as we’ve had this engine since new (but now it’s mine). Nobody around here including my family has ever changed anodes because they always look fine. We always thought Lake George boats were immune from that kind of corrosion and the best because of the cleanliness of the water. I feel a little different now going forward. Thanks, C

 

[Crispin]

sounds like your water (in the slip?) is basic
View attachment 388834
salt water is generally more conductive, but there is likely stray current in your slip, if you're in one
I would replace the anodes - you could go with a "softer" metal, see what a reputable local uses

Oh yes, sorry I got that backwards. I was thinking it might be acid rain over the years. The Lake must be fighting that pretty well to be basic. Thanks…

 

[99yam40]

you seem to have missed the part about stray current mentiond.
that can eat up metal quickly.

 

[Lou C]

That’s what it looks like (stray current) are you near docks or boats plugged into shore power?
Your OB should be tilted up when not in use.

 

[Crispin]

That’s what it looks like (stray current) are you near docks or boats plugged into shore power?
Your OB should be tilted up when not in use.

Hmm. Not really shore power but our neighbor about 40 feet away has a fully powered boathouse in the water with a fridge, lights, ice eater power and that kind of stuff. Doesn’t seem like that stuff would leak to water. Any way to check for stray juice like that?

 

[garbageguy]

some info here

https://www.powerandmotoryacht.com/uncategorized/stray-current-test

 

[dingbat]

Any way to check for stray juice like that?

Set your voltmeter to read voltage. Select AC if meter is not auto ranging.

Connect negative (-) probe to negative battery terminal.
Stick/ touch the positive (+) probe to the water and check for voltage.

If you get a reading, note voltage then switch meter over to read DC voltage.

Anything higher than 1 volt is cause for a more in-depth investigation

FWIW: Would have to be some crazy high or low PH to "eat" aluminum

 

[QBhoy]

Are you in a marina or on a jetty with power supply nearby ? Poorly earthed marina jetty can do this.
Not an engine I’m familiar with at all..but on some engines I know of…where that water is coming out…is usually where the gear oil drain screw is. Surely not the case on yours though ??

 

[Lou C]

www.boatzincs.com
has some tech data on this, they sell a reference electrode to help measure if your anodes are giving enough protection.
Also keep in mind that if you have a stainless prop it adds to the corrosion potential if the lower unit is left in the water. that's why early B-IIIs with those 2 big stainless props had corrosion issues till Merc added additional anodes.
Since my boat has always been moored I've used aluminum props and have changed anodes every season and not had a big corrosion problem with the outdrive in salt water.

 

[Crispin]

Thanks all for the insightful responses. I have not checked our slip for stray voltage but do think I should shift to magnesium anodes. I am not finding direct-fit magnesium choices for our Suzuki DF140 but I am seeing generic parts. Can I or should I bolt magnesium blocks on top of new stock zinc ones? Should I machine generics to fit? Should I buy magnesium ones and locate them wherever I can find a good surface?
Regarding the stainless propeller observation, we do have a stainless propeller so is there special anode I should place for the SS prop?
Thanks again, C

 

[dingbat]

I am not finding direct-fit magnesium choices for our Suzuki DF140 but I am seeing generic parts. Can I or should I bolt magnesium blocks on top of new stock zinc ones?

I would install aluminum anodes and see what happens.

Certainly have to provide better protection than 20 yr old, oxide covered zinc anode

 

[flashback]

You might want to check your gear lube just in case.

 

[Crispin]

Even tho I might look lame in the anode department, I do change lower unit lube every season. Thank you and I will be watching for water in the gear case.
I looked after this engine for about 5 years when we first bought it and then it went to my in-laws and a local marina. After 10 years, now it’s back with me. I’m now chasing corrosion everywhere including inside the VST housing. I realize this is probably fuel related but now seeing how bad it is everywhere else, I don’t know if it’s related to the other corrosion or not. I am blown away how bad it is. I had no idea this could happen in a fresh lake we drink out of. I’ve lived here 40 years and have seen some aluminum corrosion but nothing like this Suzuki. An electric leak in the lake seems unlikely but I am going to test for it.