So I picked up the 9' avon dingy (it's a RIB with full fiberglass bottom) and little 6hp evinrude to go along with our "new" trawler. *Everything seems good with motor but the "plug" in the RIB appears to just be a check valve instead of a true plug. *The problem is that the check valve isn't checking so very well and is letting in water! *Do they just unscrew and pop in a new one? *Pic of the offending check valve/plug is attached. *I guess i should go look online but I would guess this is a common item to replace?