Johnson motor bracket electrolysis

[Fraggle]

Every year I replace the zincs on the motor and hang a zinc guppy next to my motor bracket. I have a 2002 johnson 115 using in salt water. How do I prevent any more damage to the bracket from electrolysis. See pics. by the looks of the bracket do you think I should replace? Can the bracket be repaired? A friend said I have to bolt large zincs on each side of the bracket. Any thoughts or comments.

 

[Fraggle]

Re: Johnson motor bracket electrolysis

Every year I replace the zincs on the motor and hang a zinc guppy next to my motor bracket. I have a 2002 johnson 115 using in salt water. How do I prevent any more damage to the bracket from electrolysis. See pics. by the looks of the bracket do you think I should replace? Can the bracket be repaired? A friend said I have to bolt large zincs on each side of the bracket. Any thoughts or comments.

 

[OBJ]

Re: Johnson motor bracket electrolysis

Welcome to iboats Fraggle!

The pics didn't make it Fraggle. How bad is the damage? If it's severe, you may want to check over the rigs wiring to make sure there is nothing grounded to the boat or motor that may be causing some leakage. The engine should have ground wires electrically bonding the mid and upper section (engine). Check these to make sure they are on a clean ground.

If the boat is aluminum, make sure there is no stray wire touching the hull or anything grounded to the hull.

What kind of anodes are you using on the engine? Zinc or Magnesium? As I understand it, Zinc works best in salt water.

 

[ezeke]

Re: Johnson motor bracket electrolysis

If you have the two anodes bolted to the bottom of the transom bracket and the one on the gearcase, that is probably enough for the motor if you have checked for continuity.

One big assist is to paint the lower unit with a non-metallic anti-fouling paint designed for outboard use.

Otherwise the lower unit turns your outboard into one big anode hanging in salt water, which is a great electrolyte.

Also, using a battery switch that disconnects everything but your pumps will probably help.

 

[Vic.S]

Re: Johnson motor bracket electrolysis

Likewise I cannot see the pics.

How are you connecting the guppy to the bracket. It must have a good low resistance electrical connection to be effective.

Anodes bolted directly to the bracket will probably be more effective but you still must ensure good electrical contact with the bracket.

Is zinc suitable for protecting aluminum or is magnesium necessary?

 

[Joe Reeves]

Re: Johnson motor bracket electrolysis

Pertaining to electrolysis. Especially in salt water, that is the passage of material from one item to another. The material being removed from your engine would be deposited at some other point on your rig if your rig was the only one docked in the water, and if your rig was the one with the fault.

Usually electrolysis occurrs in the marine line, pertaining to boat engines etc, when some other rig berthed at a marina wet dock has a electrical fault. That electrical fault, however minor, would draw current thru the water which would remove metal (seems to be always aluminum) from other rigs that could be a hundred yards away. The metal would be deposited on the rig with the fault.

However that electrical fault could be traced to other sources besides boats. If it was possible to find a extensive buildup of metal where it didn't belong, that would be the culprit.

At least that's the way it was explained to me many years ago.

To my knowledge, the zink anodes are the only accessory that would combat the problem, a matter of choosing various sizes until one (or more) is found that will do the required job.

 

[Fraggle]

Re: Johnson motor bracket electrolysis

I use zincs. Any particular Brand of paint? below another pic attempt.

 

[Fraggle]

Re: Johnson motor bracket electrolysis

attempt

 

[DJ]

Re: Johnson motor bracket electrolysis

Fraggle,

Be careful painting the lower unit. Any paint on the zincs will render them useless. Also, copper based anti fouling paints will accelerate the electrolysis.

As mentioned, it is critical that you have an electrical connection between the lower unit/exhaust housing (mid section) and the engine block.

If you look, you should see a braided wire connecting the two. You can usually see it right under the lower cowl.

 

[Cricket Too]

Re: Johnson motor bracket electrolysis

I agree that if you are getting severe corrosion on a 2002 bracket, you have another problem somewhere else, either on your boat or somewhere else, that is causing it, since it is relatively new.

The one big zinc on the bracket should be more than sufficient to protect it, and if you've been replacing it every year, that's some pretty fast corroison.

My boat sits in the water from April until December, and the only anodes I have on the whole boat are the ones on the brackets and lower units, and they only need to be changed every 2 seasons.