Trim tab corrosion

[BobGlover]

I borrowed a good friend's boat with a 2013 9.8 Tohatsu outboard, and noticed his trim tab has severe corrosion; it looks like a beaver has been chewing on it! The motor is an electric start, with only a trolling motor and depth finder wired up. He's put very few hours on the motor. I've ordered a new trim tab for him, but what could be causing this problem? He recently installed an onboard charger, could this be the cause? My motors are older, and the tabs look like new.

 

[pvanv]

The tab is a sacrificial anode, so it must be replaced. If there is stray current (from a poor onboard charger), that can cause the issue. If the motor is tilted up when not running, you should get a lot less corrosion. If there are bonding problems on the boat, that can contribute as well.

 

[Scott Danforth]

My guess is a bonding error, or someone used the boat as a ground 's running a dedicated ground wire.

 

[BobGlover]

Guys, thanks a lot for the input, but what's a 'bonding error'? I wired both his trolling motor and depth finder, and did them just like I did mine. Should I check to see if any ground wires are touching the boat, etc..? Thanks again!

 

[Sea Rider]

If lower leg is left sitting on salt water for long term periods anode will eventually erode way more and faster. Better leave OB fully raised when not in use if that was the case.

Happy Boating

 

[BobGlover]

This is only used in fresh water. I'll change the anode & doublecheck the charger. Thanks!

 

[pvanv]

Automotive-style chargers are famous for leaking AC into the 12v side, causing corrosion. Ask me how I know. A true 3-stage marine battery charger should be OK.

 

[phillnjack2]

what is the anode made from ? is it for salt water or for fresh water, there are two types.
either one will corrode faster than normal if its the wrong one.
some of the anodes that are supposed to be for both conditions corrode very fast compared to the single use ones..
I would not worry too much as these are a very cheap item and it sounds like its doing its jib very good.