Do I need to replace the zinc?

[hitchhiker]

I have had my SunCat on the sea for about a year.  I haven't lifted it on the ground to check the bottom of the hull, so I don't know how much the zinc in the centerboard eroded.  If the zinc has eroded much, I have to order one before it docks in.
Does anybody know how often you have to replace the zinc if you keep a SunCat on the sea?

[Craig Weis]

Hi Hitch...I guess the loss of a sacrificial anode depends on how much electrolysis is going on under water.
A huge contributer to these things working there way out of existence during the ion exchange is;

1~How well the electrical system is grounded on board. And on dockside. And how well in sync these groundings are.
2~How 'proper' any shore power is brought on board via dock extension cords, and any additional plug-in power.

More then a few people have had there boats damaged by docking next to a 'badly grounded boat'. Plus
More then a few people have died by harbor swimming or falling in next to a 'badly grounded boat'.

Interesting side bar: A guy in Floriday who put in 'in-ground- pools with underwater lights' developed the the GFCI [Ground Fault Circuit Interupter] because so many of his customers died before his pool was paid for. Well you get the idea.

If less then 3% [I think] of the juice going 'in' does not come 'back' the circuit breaks and will not continue to make. Saving the pooler's. I was in a pool once where I could feel the pricks of electricity as I came close to the light. Very interesting.

Additionally the same thing through a pair of heavy torch cutting gloves when using the 'Mexican Smoke Ratchet' to cut through 4" electrical conduit that still had 480 volts still in it in an abandoned factory shut down for years. It was suppose to be off. I was dumb enough not to meter check.

The electrical flow went to ground right through the flame of the torch and into my hand. This is basis of the industrial and home furnace RAF 890 Protect Relay Flame control with flame rods used on gas burners. Some use Purple Peepers as well. That's another story.

It happens so fast that in the right instances just a few weeks plugged into 'not correct shore power' can dissolve and defeat any and all attempts to foil the corrosion problem. Even with metal that is Noble. Bronze/brass/stainless steel/zinc, all the way down to black iron. Some call black iron 'steel'.

So no way to answer this question with out a look~see or a megohm meter. Best way is to see what is left. I still have the small zinc that came with my outboard for the last five or so years. It becomes 'fuzzy with corrosion' and I unscrew it and wire brush the thing clean and screw it back on. No big deal.
skip.