Here is a new twist and I thought I had seen it all when it comes to Galvanic Readings.

This is the first year where ice in the marina has become a concern. This year I had close to 6 inches locking my M in tight. I began to panic a little when my shaft packing began drippin. (both developed very slow leaks and might have been from pressure on the hull)

Ok ...I put in a brand new Kosko 1/2 HP D-icing unit. It is slung under the hull at midship. It worked great and the boat was free in only a few hrs.

Now this is what I noticed. When the unit is on my CAPAC reading drops to .62. I turn unit off and readings return to my normal .92 reading.

This is an AC unit running through the ships electrical and through the galvanic isolator. It is also GFIC.

? Is the unit causing the lower readings when turned on because of?
A) Loss of potential which would be a potential corrosive condition or..
B) The turbulance created when the unit is running. (I know my CAPAC readings are way off under way)

Note: Readings are normal with unit off but submerged so it is NOT a disimular metal situation since the unit is isolated from the the hull except for electrical connection which again is grounded properly through the galvanic isolator.

Thoughts?

I figure I will not have the unit on for long periods of time. The ice is clear in my slip now and may not return unless we get another nasty cold snap.

dave

Sounds like you have a slight voltage leak, or somewhere you are inducing a current into the hull, wiring, or Capac circuit. I'd first check that connections are all dry. Good luck, Ed

Dave, It might be because the bubbles are creating air pockets around the sensor, therefore the sensor will not see solid water. Rick

The D-icer or other trade name of Ice Eater is a very simple solution used for many years around docks, boats ponds etc.

It consists of an electric motor with a propeller that pulls water up from lower depths to the surface. This warmer water melts surface ice and circulates.

I agree I did more tests and there is absolutely NO voltage leak. I show no stray AC current and if there were any the GFIC would also be tripping.

The unit is slung under the boat about just below the keel mid ships which puts it very close to the CAPAC Cathode.
I moved the unit after and the readindings moved up and lowered it and the readings also changed.. so it must be effecting the readings due to turbulence. I am no longer concerned about it but thought it was interesting. After mky first post I remember checking readings while the boat was in motion (just idle spped) and the readings drop significantly. So just a false reading. Also the 1/2 HP motor the electromagnetic interference may also have an effect on the readings when it is running.

Hi Doug.. no problem but it did scrape up the anti fouling paint a bit at water line.

Ice is out and I doubt it will freeze in again this year.


dave

Docsnow,

It was interesting. I always pull my shaft packing glands up a little to insure no drip during the off season.

Prior to ice.. the bildge was completely dry. (under a covered dock) Once the ice reached more than 4 inches I checked the bilger and noticed a VERRY slow drip from each gland. (one drop every 30 seonds)

Making no adjustments.. I put the ice deather in and the ice was gone in less than 8 hrs and next day I checked shafts and NO drip what so ever!

safe boating,

dave

My packing glands aren't dripping at all, OH Yea, I guess they wouldn't up on stands.

Sorry, I couldn't help my self.

Roger

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The trouble with getting old, There is a lot of info in memory, I either can't find it or don't trust it if I do!