Interlux VC17 bottom paint--dicolouration or blistering

[ks65609]

We have always used vc17 bottom paint and always in fresh water. In the same marina for years. This year's haul out presented us with some type of blistering or apparent damage to the bottom paint in the areas of the trim tabs and centre anode. All anodes were replaced this year with magnesium. We have never had any issue such as this. The marina as well is in the process of trying to figure out what may have occured. Our slip neighbours do not have any type of similar situation. I would sure appreciate any input or feedback from anyone with experience in this area. We spend considerable time and effort trying to keep our boat in top condition and find this very disturbing. There is no apparent damage to the gel coat.

Thanks very much
Ken
http://s1091.photobucket.com/user/ks65609/slideshow/92 330 sundancer
http://s1091.photobucket.com/user/ks65609/media/92 330 sundancer/IMG_1935.jpg.html?sort=3&o=1

 

[Fred]

This looks like a stray current issue. I would check that your galvanic isolator is functioning properly and that your bonding connections are solid.

 

[ks65609]

This looks like a stray current issue. I would check that your galvanic isolator is functioning properly and that your bonding connections are solid.

Thx.
I am not knowledgeable regarding these items, however I will ask the marina technicians to take a look.

Ken

 

[480ces]

My Formula had the same issue. VC17 will look just like that when exposed to stray current.

For me it turned out to be the lead that connected the fan to the main board on the battery charger. It had come looose and the insulation abraded by the fan. This left a single strand of wire in contact with the frame and dumping DC out into the bonding system. Not enough to really eat the anodes but the bottom paint sure showed we had an issue.

 

[ks65609]

My Formula had the same issue. VC17 will look just like that when exposed to stray current.

For me it turned out to be the lead that connected the fan to the main board on the battery charger. It had come looose and the insulation abraded by the fan. This left a single strand of wire in contact with the frame and dumping DC out into the bonding system. Not enough to really eat the anodes but the bottom paint sure showed we had an issue.

I did not even think it could be something on our boat. I may have dislodged something when cleaning the engine compartment or elsewhere.
Thanks very much for the input.
Ken

 

[480ces]

The first place I'd look is the galvanic isolator. You'll see this paint issue if its gone bad.

You need to disconnect it to test it, its pretty easy if you have a multimeter. There are multiple youtube videos that show exactly how.

 

[ks65609]

The first place I'd look is the galvanic isolator. You'll see this paint issue if its gone bad.

You need to disconnect it to test it, its pretty easy if you have a multimeter. There are multiple youtube videos that show exactly how.

According to my boat's manual, it should have a galvanic blocker DC current (manual description), however does not show clearly where it would have been installed. Would you happen to know the specifics of where I may locate the unit? I do not know if a galvanic blocker is the same as a galvanic isolator.

Thanks very much again
Ken

 

[480ces]

Galvanic Isolator and Galvanic Blocker are interchangeable terms. I'm not positive where it would be on your boat. Someone with a similar model may chime in. They are usually near the DC Panel but it can really vary.

A call to Sea Ray might also yield an answer.

 

[ks65609]

Galvanic Isolator and Galvanic Blocker are interchangeable terms. I'm not positive where it would be on your boat. Someone with a similar model may chime in. They are usually near the DC Panel but it can really vary.

A call to Sea Ray might also yield an answer.

Thanks for the clarification. The illustrations in the manual point to the shore power inlet/main distribution panel. I have contacted Sea Ray in the past with excellent results and thanks for reminding me of that source as well.

Thanks again for your help
Ken

 

[ks65609]

UPDATE TO TRANSOM CORROSION ISSUE:

I am updating my post as to what has taken place over the last few months:

-marina has tested our boat, surrounding boats, as well as the marina electrical systems- all is good
-marina has sanded and cleaned affected areas and applied a new coat of Interlux VC 17. Before doing so and area one inch wide was taped off around the trim tabs and transom anode to ensure the bottom paint did not contact any of these areas. I thought this was a very professional approach to resolving the issue
-an area of corrosion has formed again around the transom anode, however not the trim tabs !
Comment:
I could be wrong, however I believe this entire issue started when the existing anodes where changed out and magnesium installed.
I am also concluding (maybe incorrectly) the magnesium anodes and VC17 are not compatible.

This is a very frustrating problem !!!

http://s1091.photobucket.com/user/ks65609/library/corrosion

 

[480ces]

I've never considered it, someone else may know though. Could the Mg anodes be too protective for the water you're in? I see you're also Ontario based so it's gotta be fresh water and Mg should be right choice.

Are there anodes on your tabs? Have you check DC to Bonding for a current leak?

 

[ks65609]

I've never considered it, someone else may know though. Could the Mg anodes be too protective for the water you're in? I see you're also Ontario based so it's gotta be fresh water and Mg should be right choice.

Are there anodes on your tabs? Have you check DC to Bonding for a current leak?

Thank you for your feedback. To answer your questions the trim tabs and prop shafts have the mg anodes as well. The boats has been tested for current leaks and all is good.

UPDATE AS OF TWO DAYS AGO:
I contacted Interlux directly and was very surprised to receive almost an immediate response. VC17 cannot come into to contact with any other metal, period. They recommended leaving a unpainted space around all metal connections to the transom, thus the space around the trim tabs and fasteners for the centre anode, just as the marina had done. However two additional suggestions were offered as well. First, leave a larger unpainted space around the centre anode ( I would imagine due to the physical size of the anode). Second, coat the unpainted area with Trilux 33. I have passed this info along to my marina and we will implement both next spring. Hopefully problem solved.

HOWEVER,I have learned a valuable lesson. If your anodes look like new each year and you are thinking no need to change, big mistake. It means they are not doing a thing.

Thanks very much for your help
Ken