Pontoon boat left in water for 3 weeks when I pulled it out had tan crust in chicken pox pattern below water line, comes off easily but pits
Fresh water lake, looks like a deposit, sandy after it dries. Area had been hydrilla treated, but was told treatment would not cause this.
I'm no chemist, but I'd believe the hydrilla treatment guy. If the water had checmicals in solution it probably would have produced an even pattern rather than a spotted one as you describe.
Is the boat new or used? How long have you had it? Without more information I'll posit the scenario that someone previously cleaned the tubes with acid, didn't rinse it thoroughly and created pits. Then when you put it in the water, the plant growth gravitated to those little pits making them stand out( plant life loves little nooks and crannys)
Again, provide some more info about the boat, and we'll try for a better answer.
Another question? Are you using a battery charger aboard? And are any of your ground wires perhaps touching one of the toons? That too, could create the same scenario above.
Thank you for your response. The boat is new, about 6 months old, has not been in water more than 2 consecutive days at a time. The only chargers on board are 2 solar panels connected directly to the battery.
Our neighbor was down this past weekend and he suggested that it might be fresh water oysters (or their seedlings?) does this make sense?
No. I mean the growth may be the oysters your buddy referred to, but I never heard of a bivalve creating pitting. I'd look to your electrical system.
Also, the growth and the pitting may not be related; they may be coincidental.
Check for current leaks, particularly for "always" on components like your bilge pump and those solar panels. Could be chafed wiring, a ground connection touching boat,etc....here's an article that will walk you through the process
If you come up empty there--are there any other boats at the dock? Do they have shorepower? Is there any 110-volt service at the dock?
From here, your problem "looks" like an electrical one.
Sorry to get back to you so late. Read the troubleshooting and did the test, came up with nothing, no electricity at dock and the other two pontoonboats have the same spotting. I have had a chance to research the hydrilla chemicals and they will produce a salt compound if water temperature is just right. But whatever it is, it is hard to get it completely off. I scrubbed it off and then power washed it and it appears to be coming back in certain spots (the boat is not in the water ) I guess from the rain is enough moisture to get it going again. My next step is to put an aluminum polish on the pontoons. Thank You for your response.
PS: Talked to a local boat repair shop and they have seen this and feel that it is from hydrilla tretment.
DGB -ANSWER: Tallked to a Hydrilla specialist that has been hired to monitor the lake. He told me that the hydrilla treatment has copper sulfate in it which is a salt that acts just as if you had the boat in salt water and of course copper and aluminum will set up electrolysis. So you have two things working against the aluminum; magnesium anodes can help but just help. Also, the salt crystals keep coming back; this is after power washing it and then using an aluminum compound polish on it. A person in a boat shop that has had first hand knowledge said that he has heard of putting white vinegar on it and polishing. It will keep it at bay for a couple of years, but once it has gotten on the aluminum it will keep coming back. I guess the answer is: if you think that Hydrilla treatment is going to occur, get the boat out of the water. This is another good web site on electrolysis http://intermarineboats.wordpress.com/2012/03/12/a-bit-on-galvanic-corro...