Uncovered boat and found several small dark spots on the vinyl surfaces, not mold or mildew, hard to clean off and leaves a yellowish spot when done, anybody know what is causing this, insect of some type I think?
it's spider dung (crap). Look above it and you will probably find some spider or cob webs (they could be very small). I usually take it off with my finger nail and a little water. The sun will bleach the yellow remnants out.
Hi. It’s almost certainly spiders crap. Hard to get the marks out but if you are careful using mechanics type hand cleaning wipes (I use wonder wipes) then it comes off.