Are you guys exceeding the weight limit on the boards?
OK, the boards shouldn't be cracking, my 2002 boards are gray and just the same material as the floor boards beneath the leaning post and behind that. I have a small hole in the floor board convacity which allows water to drain to the bilge if the running boards were to leak.
I had in the past, sealed the boards with Rule Elastomeric and used ample amounts to fill the gaps to create a smooth transition between the boards and deck.