Trim tab corrosion

BobGlover

Seaman
Joined
Jul 27, 2003
Messages
65
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

Admiral
Joined
Apr 20, 2008
Messages
6,500
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

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,310
My guess is a bonding error, or someone used the boat as a ground 's running a dedicated ground wire.
 

BobGlover

Seaman
Joined
Jul 27, 2003
Messages
65
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

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
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

Seaman
Joined
Jul 27, 2003
Messages
65
This is only used in fresh water. I'll change the anode & doublecheck the charger. Thanks!
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,500
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

Ensign
Joined
Apr 30, 2011
Messages
918
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.
 
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