My 98' 340 has one of those helm seats that fold down onto the swim platform. Two of the ss screws that hold one of the hinges to the transom are loose and I can't figure out how to fix them. Tightening with a screw driver does nothing. They appear to require a nut or maybe a backing plate as they have a flat rather than pointed end, but I cannot get to the other end?! I have tried reaching in from the swim platform compartment, the stern lazarette in the cockpit, and by removing the wood panel from inside the aft cabin, all to no avail. Does anyone know what I need to do?