Electrolysis check for Swift Trawler Owners

[bglad]

I recently had a look at a 2014 model. See below:

Sorry to bump this old thread... just bought a 2015 Beneteau Swift Trawler 44... noticed that my AC thru-hulls look problematic... I have to check the rest when I get back to the boat...

After reading this thread, I have some additional questions...

1. Where does the rudder zinc go? Any picture or part #? I don't think I saw any zincs on my rudder when I had her hauled during purchase survey...

There was no zinc on the rudder. Zincs were installed on bow thruster, propeller nut, trim tabs and bar type on transom. Bar zinc is attached to rudders by internal cabling

2. What was the final verdict on adding a bonding system to this boat? What should be connected?
Underwater thru-hulls were not bonded and looked fine.

3. I do not know if I have a galvanic isolator...any easy way to check? Someone told me the ST44 has an earth ground and therefore a galvanic isolator would be useless? Would like some further opinions on that...
This boat's owner installed a galvanic isolator to reduce excessive zinc depletion that was occurring in his marina. Isolator solved his problem. Trace your shore power cabling and see if you can sight an isolator. If not plug your shore cord into your boat and bring the dock end inside and perform this test: Testing A Galvanic Isolator Photo Gallery by Compass Marine How To at pbase.com If you show less than one ohms resistance then there is no isolator. If you get readings similar to what are shown in the Compass Marine Article then you have one. Of course make sure all AC power is off aboard including generators, inverters or others before attempting this test.

Thank you all!

 

[sunchaser]

No underwater through hull bonding system?

 

[Steve DAntonio]

The bonding system question is one that can be endlessly debated. From my perspective, they offer far more benefits than not, however, most French and many other European vessels I inspect are not built with bonding systems, and if they are present they are isolated; which again can be debated. This relatively short article explains how bonding systems work and why it's important that they be interconnected with AC safety and DC negative systems Bonding Systems and Corrosion Prevention | Steve D'Antonio Marine Consulting

If you know how to use a multimeter, you can test for the presence of a galvanic isolator. Otherwise, out of necessity, they are nearly always installed near the shore power inlet. This article shows some photos and explains how they work. “Zinc” Anode Selection and the Role Played by Galvanic Isolators | Steve D'Antonio Marine Consulting

Not sure about the 'earth ground' comment. The DC negative and AC safety ground should be common or connected for electrocution prevention purposes, and thus they are referenced to "earth" or dockside ground, and thus the grounds of all nearby vessels that are also plugged in to shore power. IMO, every vessel with shore power should be equipped with a galvanic isolator (at least, if not a transformer), to prevent nearby vessels from consuming your anodes. It's cheap insurance.

Rudders that are part of a bonding system, which is connected to an anode, do not necessarily need their own anodes, however, there's no harm in having them there as well.

 

[Mr. Blu]

Happy New Yaer to everybody on the forum.


We bought last year a seven years old ST 52 so therefor I looked with some interest at the discussions and remarks in this thread.

If galvanic corrosion should be a common known problem with the Beneteaus ST surely it would have been mentioned by the surveyor. I also read a survey report on another ST 52 and in that report it was not mentioned either. And allthough all hull-thru's were clean when we made our boat ready for winter, the remarks in this thread are surely reason for me to mount a 32 A galvanic isolator to "disconnect " the boat from leaking currents from the shore (as far it is not mounted already).

I will have to check this out next time we visit the boat, because we live in the Netherlands, approx 1.000 miles away from the marina.
We (cruising in Croatian waters in the Adriatic)) often visit other marinas and we are not sure that all marinas in Croatia have the same electrical standards regarding their shore power units as in our homeport.

However still I find it strange that a rather inexpensive (in relation to the total cost price of a boat) device like a galvanic isolator is not a standard item to be part of a boat when bought new.

Regarding the bonding: We owned a President 385 Sundeck (with a poor electrical system due to alterations by previous owners). There was a lot of corrosion on the shafts before we mounted a bonding system. So for the President it had a hugh effect.

Regarding the anodes: it cannot be emphasized enough they are very important because of their sacryfing nature and should be last in the chain of current. Better too many than too less.
Regarding Beneteau: this is the way to do it when you are confronted as important manufacturer with a new problem. Look at it yourself.

Greetings,

Paul Marsé

 

[boater3]

So I poked around where the electric comes in from shore. There are a lot of boxes. Half seem to be differential circuit breakers. Looks like these would serve a different purpose than a galvanic isolator correct? For those that have added the galvanic isolator to their ST44, which model did you go with? If you have a single 50 amp connection but it breaks off to two panels, do you need one or two galvanic isolators? Thanks!

 

[bglad]

The "differential breakers" are residual current devices that trip for stray current of the AC (deadly) type. A galvanic isolator(s) blocks current at potentials that cause galvanic corrosion. I wonder if two (one for each shore cord) rated at the cord amperage would give more protection from galvanic corrosion. Current blocking capability x 2 versus one. Would be a good question for tech support from manufacturers of any of the available devices. The overall rating of 30, 50 or 60 amps would be to insure the current carrying capability of the device in the event of a dead short (once again deadly AC current).

Attached is a little additional information from DEI on the subject.

So I poked around where the electric comes in from shore. There are a lot of boxes. Half seem to be differential circuit breakers. Looks like these would serve a different purpose than a galvanic isolator correct? For those that have added the galvanic isolator to their ST44, which model did you go with? If you have a single 50 amp connection but it breaks off to two panels, do you need one or two galvanic isolators? Thanks!