Electolosys

[Freestyle]

I got a call from my dockmaster stating that they had measured all of the boats in the marina and my boat was putting out 900mb of electricity. I asked how they measured this and he said they measure the output of the boat with and without the electric turned on. I need to go down there and investigate some more but hoped to get some advice as to the measurement and probable causes. A couple other factors:

1. My boat has a massive transformer hanging over the water bewteen my slip and another boat. They just did a bunch of work on the transformer. Any merit to getting them to test the boat at another location?

2. My zincs are good and have not been replaced in 1.5 years. I would think if I was an electolosys problem my zincs would be wasted.

3. I noticed a loose grounding strap below the port main engine a few weeks ago. Could this be the culprit?

4. The dockmaster said that the tester had said that Hatteras boats frequently had electrolysis problems and in fact the other problem boat in the marina is a Hatteras. Any idea what he means?

I just have a feeling our marina hired a guy with a BS device that picked out two older boats and said they had a problem but maybe I am just defending a loved member of my family here.

Thanks for your help

Bruce

Freestyle
1976 43 DCMY
Tampa

[yachtsmanbill]

Hey Bruce... start reading! There is a MYRIAD of situations to consider when reading the meter. My aluminum Roamer was being the sacrificial anode while protecting the steel dock a while back. The marina's juice was leaking; not the boat. The people to contact are Yacht Corrosion Control Consultants.
They will sell you a silver chloride half cell which is what goes into the water next to the boat and a Milliamp meter to the boats ground for your readings.
Hope this helps, somewhat! ws

http://docs.google.com/gview?a=v&q=c...ts&hl=en&gl=us

[captddis]

I got a call from my dockmaster stating that they had measured all of the boats in the marina and my boat was putting out 900mb of electricity. I asked how they measured this and he said they measure the output of the boat with and without the electric turned on. I need to go down there and investigate some more but hoped to get some advice as to the measurement and probable causes. A couple other factors:

1. My boat has a massive transformer hanging over the water bewteen my slip and another boat. They just did a bunch of work on the transformer. Any merit to getting them to test the boat at another location?

2. My zincs are good and have not been replaced in 1.5 years. I would think if I was an electolosys problem my zincs would be wasted.

3. I noticed a loose grounding strap below the port main engine a few weeks ago. Could this be the culprit?

4. The dockmaster said that the tester had said that Hatteras boats frequently had electrolysis problems and in fact the other problem boat in the marina is a Hatteras. Any idea what he means?

I just have a feeling our marina hired a guy with a BS device that picked out two older boats and said they had a problem but maybe I am just defending a loved member of my family here.

Thanks for your help

Bruce

Freestyle
1976 43 DCMY
Tampa

I am going over to the Bella Donna tomorrow as marshall told Doc the same BS. His zincs go a year also and the boat has isolation transformers. I don't think they know what they are talking about. I am ready for battle, but Doc is ready to cave in and put zinc savers on even though they are not needed. The person who ran the tests says he will install then!! NO WAY.

[Pete]

Been around this electrical stuff a long time and have not heard of "mb" so I going to assume it is "mv" (millivolts) we are are discussing. You need to better understand what they are measuring. The 900 mv sounds right on for one common test, but do not know if that is what they have.

The common test is the electrical potential of your bonding system versus water ground. A large fiberglass boat should be in the -750 to -1000 mv DC range when measuring from its bonding system to a half cell in the water close to the boat. When doing this test the shore power should be disconnected and any other shore connections such as cable TV. A -900 mv result would tell you the zincs on the boat are working, as in just the right amount, and purity, for your application.

If they are trying to measure something else the group will need to know what and how they are doing it.

Hope this helps. Let me repeat, at this stage it is very important to not only shut off shore power, you absolutely need to be totally disconnected from anything on shore to get any accurate/useful results.

Pete

[REBrueckner]

If that is what your dockmaster reported, he has NO IDEA what he is talking about. Yet, he may be trying to help...

Post #4 is correct. To repeat: The results the yard observed appear indicate your zincs ARE protecting your underwater metals as required. All is well.

As an example, a typical manganese bronze prop will freely erode (corrode) without any zincs present, producing a voltage of about 450 mv. This is in seawater at 75 degrees. With nearby zincs present, the zincs will instead erode, protect the valuable prop, and present a voltage in the 900mv range.

The Yacht Corrosion Control test meter and accompanying book are excellent..I've used them for many years. But INSTEAD of spending unnecessary money, try instead going to YANDINA MARINE ELECTRONCIS at

www.yandina.com./electrolysis.htm

and printout out a few copies of the EDUCATION ON BOAT ELECTROLYSIS. It's a quick instruction on electrolysis and how to make tests with an everyday multimeter which you should have aboard and know how to use anyway. Make the tests and give them with a copy of the instructions to the yard. This is the same site I have recommended for years.

[captddis]

Checked the 61 today. Both shore grounds were 850MV with nothing on. Turned everything on one at a time and no changes on the AC or DC side.
The boat goes close to a year on zincs. I see no problem. Maybe over zinced a little?

The shore grounds ARE connected to the DC bonding at the ER buss. The print on the boat confirms that this is the way it left the factory.

[REBrueckner]

"Checked the 61 today"

Sounds just fine...one normally expects about 850 to 900 mv.....depends on temperature and salinity so all appears well....more of each leads to slightly higher readings....salinity is likely the more significant factor....

[34Hatt]

Checked the 61 today. Both shore grounds were 850MV with nothing on. Turned everything on one at a time and no changes on the AC or DC side.
The boat goes close to a year on zincs. I see no problem. Maybe over zinced a little?

The shore grounds ARE connected to the DC bonding at the ER buss. The print on the boat confirms that this is the way it left the factory.

So checking the boat was the easy part and was just as you figured!

But how did you make out with the Knuckle heads at the Marina
That usually is the hard part

[Pete]

If I am reading the results correctly, they are excellent. First with all shore wiring connections removed, you get -850 mv (boat to half cell). Then when you connect everything back to shore and tie into the dock grounding system, nothing shifts, that is great, a first for me. Given the wiring of the boat with the dock ground connected to your bonding system, that would say that on average everyone on the dock is properly protected with zincs and there is no DC leakage on the ground from any boat. Good neighbors.

Pete

[Freestyle]

Another thought, when they tested my boat they turned off the shore power. My inverter automatically comes on whenever shore power is turned off. Could the inverter affect the reading?

The hard part in all of this is going to be persuading these guys that their expert tester the isolater salesman may not be infallible.

Thanks

Bruce

Freestyle
1976 43 DCMY
Tampa