I've been layering the 'Marine Strip" on the boat to get rid of the yellow gloss, which took me down to the original blue anti slip, but in parts that has come up and Im getting patches of what looks like a maroon coloured filler underneath. Is this what should be under the paint or does this mean some serious repair work has been done under there and I need to get all the blue off to make sure its not a contender for my leak problem??
Hard to see but it only looks like previous non-slip paint.
But really - don't worry so much, you are doing fine and a new paint system will cover up all that paint and if at this stage you cannot see holes or cracks I'd say you are good to go.