Marinette Boat Forum

I have noticed a lot of variance in my Capac readings this season. My anode setup is exactly as Marinette recommends for a 28' single screw. I polish the anodes at the beginning of each season to remove all the junk.

It seems in shallow/warm/dirty water the Capac reads as low as .8

When I move to deeper/colder/cleaner water, readings come back to the normal range. Luckily at my slip the readings are usually normal, if not a little high. Any way to correct/prevent readings that are too high?

Does this seem consistent with what others have experienced? BTW the readings I listed above have occurred in the same day.

I'm going to venture a guess that you have correctly diagnosed what's happening... water clarity could have an effect. Doesn't sound like a loose conection because the behavior is consistent. How high is too high?

Your numbers are well within normal range. Fresh water will produce lower numbers (remember your CAPAC readings are Neg. Milivolts) Pure water is actually an insulator. Changes in PH will also effect your readings. Fresh anodes making clean contact to the hull (Aluminum Alloy) in fresh water will usually be less than .95 and should not exceed 1.05. While higher and lower reading will sometime show it may be temporary and being caused by outside influences around the dock.

Readings underway generally not reliable. Personally I have found using a MAG anode off the side while in my slip helps keep readings more stable.

Insure your Shafts are properly isolated this is easy to verify with a jumper wire from shaft to hull. If CAPAC reading deflects downward when you ground your isolation is good. If not your shafts are not isolated. Rudder posts seldom are completely isolated due to steering linkage. This is not a big concern since anodes should be on each rudder blade. Your rudder bushings are non metallic and help reduce continuity.

Safe boating,
dave

My prop shaft is isolated from the hull with a Globe Drive Saver. The shaft also has an anode on it, just because I am paranoid. It's $7 peace of mind.

I have also isolated the rudder. I used a combination of nylon washers and heat shrink tubing on the rudder linkage components. The rudder also has anodes and brand new nonmetallic bearings.

I just pulled the boat on Friday to do some other projects. Will splash in about a week and continue monitoring this.

jralbert - the highest reading I have ever had at my slip is 1.1, maybe a hair over that.

No apparent corrosion problems at this time.