Galvanic Corrosion

[The Islander]

Hey Guys,

I recently purchased a 2008 26M with a 2023 Suzuki DF60A engine.

The boat and motor was in Florida salt water for about 6 months in 2023. Then it was trailered next to the marina, out of the water for about a year until I bought it.

The condition of 3 zinc anodes are as follows. Trim tab-great, Rod tab-good, Bar-poor.

The aluminum structure, on the engine below the water line shows considerable corrosion in and around the Rod tab and Bar area. For a boat and engine that was only immersed in salt water for 6 months this corrosion on the engine mounts seems to be excessive.

No copper infused antifouling paint was applied to the engine mounts.

What are your thoughts on how an excessive amount of corrosion could happen within 6 months?

Thanks,

Ed

[Be Free]

When you say it was "in Florida salt water for about 6 months" do you mean it was was actually floating in salt water for that time?

If it was in the water and if it was plugged into shore power then you may be leaking current into the water. In addition, if it was in a marina the problem could have been caused any nearby boat in the marina.

It's a good idea to get your motor out of the salt water as much as possible when it's not being used; doubly so if you are in a marina.

[The Islander]

I may have determined a reason why the anodes on my Suzuki DF60A did not do a good job on reducing corrosion to the aluminum structure below the waterline.

Since it is not recommended to paint the anodes, thus leaving them exposed to potential barnacle growth, they become covered with barnacles very quickly.

There was a lot of barnacle growth on the anodes when I bought it last month. I am guessing that with the anodes covered with barnacles, that reduces the effectiveness of the zinc anodes.

Yes it was in a marina, actually sitting in the salt water for about 6 months. It was probably connected to shore power as all of the other boats are also. I just bought the boat.

I understand that electrolysis created by other nearby boats could have been a contributing factor also.

[Hamin' X]

What kind of anodes did your motor have? Saltwater anodes are different from the ones for fresh.

[Russ]

As mentioned above, different anodes for salt.

Also, that motor has INTERNAL anodes.

https://www.boats.net/product/suzuki/55320-94900

[The Islander]

It came from the factory with zinc anodes in all 3 locations.

I know that freshwater requires magnesium. Saltwater is suggested to have either aluminum or zinc.

Is it possible that with the attachment of a Raymarine Auto Pilot system, both the rudder plates and aluminum motor brackets could be prone to have more corrosion? Electrolysis and or Galvanic corrosion being more prevalent in the area where these two metals make contact with the saltwater.

There was a lot of barnacle formation on the factory bar and rod anodes. I am thinking that the calcium buildup brought on by the barnacle formation over a period of 6 months being in warm saltwater was a contributing factor to excessive corrosion to the aluminum motor brackets and area between the stainless steel screws and rudder mounting plates on the transom.

Thoughts?

[Ixneigh]

I had to put extra zincs on my motor within a year of purchase. The power tilt and motor mounts showed corrosion. In my opinion, the stainless rudder hardware is the culprit. It’s not passivated because that would cost money, and mine developed a whitish coating after a while. The good thing was my motors aluminum was protecting the stainless steering gear! So the extra zincs helped a lot.

Ix

[Russ]

Our boats came from the factory without a motor (or jib or.....most things).
The dealer installed the motor and the motor came with anodes already attached.

The barnacles could have been interfering with the anodes' purpose.

Stray electrical current is the most likely cause of your corrosion. That could be from a neighbor's boat or the marina's electrical system. It could be from your boat, however, unless there is some funky wiring going on, I doubt it. Your AP is not likely to do with any of it.

My dad used a zinc "fish" on his boat. He would clamp the clip to the propeller shaft inside the boat and hang the "fish" over the side for extra protection.
I would probably get something like this to supplement the motor anodes.

https://www.westmarine.com/martyr-clamp ... 88558.html