So I have this light brown line around my fin box on my ultrasonic, can't remember it appearing but it's been there for a few months at least. Seems water tight. Should I worry

If its soft and you can stick a knife into it , id worry.
Just tried that, I can get the point of a very sharp knife to go in about half a mm at the most then it feels solid.
I'd do a leak test. With a paint brush , keep applying soapy water on the area with the board in the sun with the vent closed.You will know within a couple minutes. If there is bubbles , it will need repair. Hose off all soapy water from the wound if it is leaking . Hopefully it's just bog and don't worry about it ![]()
I'll be very sad if it's dead, the ultrasonic is my favourite and most used board. The otherday I left it in the sun after sailing with the vent plug in. When I took the plug out air hissed out as well so I guess that means it's air tight and no leaks.
It's just wear on the edge cos filler n paint doesn't like plastic
on many boards the edge is routed back with a 45deg trim bit to stop glass lifting at the edge so u prob have that goin on too
Thanks guys, sounds like I'll keep using it and I'll just check now and then for water. It's this time of year when I'm starting to pack stuff up for winter I notice all these things.