jim,

i see that you have not had any replys......and i suspect that may becuase your situation is pretty unusual....

that said....i am at a bit of a loss to understand what has happened here....and i have only seen something like this once before....so i am going to go out on a limb.....

i don't think what you have here is typical water intrusion.  water intrusion is usually accompanied with staining and darkening....and in a lot of cases...a bit of mold....which sometimes leads to a dark/blackish mark.

what you have here appears to be more of a 'bleaching'.  the wood has natural oils that are important to the colour of the wood.  when you build and ecapsulate in epoxy, that should all be locked in.  there are two ways i have seen that you can get bleaching.....an exposed piece of wood and exposure to sun (think teak...and the what it looks like if it is not oiled or varnished) or a chemical bleaching....which could come from any acidic fluid or exposure to sea water than drying.... I also had this happen once  to me on some okoume that a cat peed on

as for what you can do now....a couple thoughts.

first, i would inspect the interior of the boat carefully and confirm this is limited to this area and that you don't have any unsealed wood or anything else unusual...and let us know what you find.  use a mirror and flashlight to look up underneath the deck and particularly around this blotch.

second, the repair....i would start with trying to do a spot repair and see how that comes out.  the easiest/quickest thing to do is to sand the glass off in the area and stain to match....or at least get it closer in color than it is now.  reseal with expoxy and a glass patch.   this will probably be just fine if done with some care and you will probably notice more than anybody else. 

alternatively, there is stripping the glass off the entire section, sanding and re-staining......which may allow for a more uniform look.   and i have even seen whole panels cut out and replaced....obviously these other approaches are big efforts.

hope this is helpful.

howard

Thanks, Howard. Option No. 1 is what I plan to do. The boat is due for a new coat of varnish this year anyway, so before I do that I'll sand, spot-stain, and re-glass this area. By the way, this is one of the Ducklings I bulit for a grandson, and I guarantee he'll have just as much fun with the blotch as without it. In fact, we plan to go for our first paddle of the season tomorrow, with blotch.

Jim