Anode trim tab question

[Douglasdzaster]

Just received a new anode trim tab. It doesn’t give me any information about what alloy it is and I’m not sure I can tell. My boat goes to freshwater only so I wanted magnesium or at least aluminum. I’m afraid they sent me zinc.
Could y’all look at the pictures and see if you can tell? I sure would appreciate it.

 

[airshot]

For freshwater only, not sure it would make a difference...however, can't say for sure from the pic.

 

[LDUBS]

I sure can't tell what it is. Zinc is commonly used for outboard trim tabs. I'm not following why zinc be a last choice. Seems zinc would provide good protection. Seems to me aluminum wouldn't be wanted if your objective is to protect aluminum from galvanic corrosion. Isn't the objective for the anode to corrode instead of the motor? What am I missing?

 

[airshot]

Different materials errode at different speeds. Based on water quality and content, aluminum can be slower where zink can errode fast. Not sure what the posters reasons are, but my experiences have had to do with the water types and what best material to use.

 

[flatheadsteve]

I have always used zinc anodes because I go into brackish waters sometimes. With this year's drought those areas had the highest salinity levels in decades.

 

[LDUBS]

Different materials errode at different speeds. Based on water quality and content, aluminum can be slower where zink can errode fast. Not sure what the posters reasons are, but my experiences have had to do with the water types and what best material to use.

Your earlier point about fresh water is supported by my experience. I check the zinc anodes on my outboard every maintenance cycle. After 5 years, they have no wear. Still, if something is going to corrode, I want it to be those anodes, so want them to be the "weaker" metal.

 

[Tin Man]

I believe Yamaha uses all three types depending on the motor. There may also be internal anodes; it would reason that you would want all anodes made of the same material. I'm sure you are using the correct anode seeing as it is an OEM anode. If it were aftermarket, all bet are off!

You could also contact Yamaha directly. I have called them in the past and they are very helpful.

 

[thill]

It's zinc-rich "pot metal" that is made to corrode before the expensive aluminum motor does.

You don't need to worry about the anode corroding the motor. The problem occurs when the anode is gone and then the motor starts to get eaten up.

Good choice, replacing the anode!

 

[airshot]

In my experience they have been made of zink for fresh water as standard. Other materials were availiable when special needs were needed, but mostly special order.

 

[Douglasdzaster]

I needed to replace the old one and while looking around I read a few articles (Here I go loosing myself in the internet again) about the different alloys. The aluminum alloy the anodes are made of is different from the aluminum on an outboard. And that it is good for backish water and could work in freshwater. Zinc is an alloy for saltwater. That left magnesium that is supposed to be the best for freshwater.

After I absorbed that information I was dead set on magnesium and aluminum for my second choice.
I didn’t research what I read to confirm. I just started going must not be zinc.

I have always fallowed y’all’s advice because you’re actual boaters andTin boaters at that. You guys know.
It’s an OEM trim tab and part number is correct for my outboard.
After reading the replies I’m going to use it. I was trying to make sure what I used would get eat up before anything started on my outboard.
Some of you know about the rebuild on this boat and know how I feel about corrosion after that.
I do appreciate the input. Y’all have straightened me out more than once by pulling me out of a few rabbit holes I was headed down by making me realize I was about to do something that wasn’t necessary.

 

[flatheadsteve]

I needed to replace the old one and while looking around I read a few articles (Here I go loosing myself in the internet again) about the different alloys. The aluminum alloy the anodes are made of is different from the aluminum on an outboard. And that it is good for backish water and could work in freshwater. Zinc is an alloy for saltwater. That left magnesium that is supposed to be the best for freshwater.

After I absorbed that information I was dead set on magnesium and aluminum for my second choice.
I didn’t research what I read to confirm. I just started going must not be zinc.

I have always fallowed y’all’s advice because you’re actual boaters andTin boaters at that. You guys know.
It’s an OEM trim tab and part number is correct for my outboard.
After reading the replies I’m going to use it. I was trying to make sure what I used would get eat up before anything started on my outboard.
Some of you know about the rebuild on this boat and know how I feel about corrosion after that.
I do appreciate the input. Y’all have straightened me out more than once by pulling me out of a few rabbit holes I was headed down by making me realize I was about to do something that wasn’t necessary.

You could always throw an anode on the hull if it makes you sleep better at night. I have 1 on my transom below the water line but only because I venture into brackish water. I think most corrosion issues on tin boats used in freshwater is from using improper hardware that reacts with the aluminum.

 

[LDUBS]

There may also be internal anodes; it would reason that you would want all anodes made of the same material.

That makes sense.

 

[airshot]

You could always throw an anode on the hull if it makes you sleep better at night. I have 1 on my transom below the water line but only because I venture into brackish water. I think most corrosion issues on tin boats used in freshwater is from using improper hardware that reacts with the aluminum.

Or, they have improper electrical hookups in there aluminum boats. Saw that on a few ocassions..

 

[Douglasdzaster]

You could always throw an anode on the hull if it makes you sleep better at night. I have 1 on my transom below the water line but only because I venture into brackish water. I think most corrosion issues on tin boats used in freshwater is from using improper hardware that reacts with the aluminum.

That’s exactly what I had to deal with when I started on the boat. One day I figured I’d remove the flooring and see if it needed a rinsing out. Floor looked good on top. No slip coving etc.

I unscrewed the metal strips and towards the bow there where old metal signs layered to make up that part of the floor the from those to the back bench in the stern was a sheet of 3/4” water soaked treated plywood. There was moisture between the signs. Moisture under them as well as where they met the plywood. I had to get a young man from across the street and my wife to pull the sheet off plywood out it was so heavy.
Then I saw the boat. Corrosion and pitting everywhere and rusty spots where the screws were in the ribs as well as pitting.

It took about a month for the abatement. I sanded and used Nyalox brushes. I found rusted screws and bolts old hooks and lures in all the channels where they ran underneath the ribs so it wasn’t draining properly. I ran a magnet under them and all of it stuck to the magnet so I couldn’t pull it out. Now if it sticks to a magnet it doesn’t go on my boat. Even the cheaper grade stainless steel hardware will attach a magnet some so it was out of the question, if it’s not aluminum I have a barrier the keep them from touching. It ended with a Dremel and tungsten bit of different sizes first to remove corroded screws broken off in the ribs then the Dremel and a magnifying glass to remove the corrosion from all the little pits. Topped it with a good coat of polish and waited 3 months.
After waiting I inspected it for anything that tried to come back luckily I got it all. That’s when I stripped the polish coated it and built a new floor.
Then I started looking at things like stern light mounts kleets and other lights all installed with the wrong hardware so I have cleaned and replaced every piece of hardware that was on the boat.