I believe they are thru bolted, so you need to take the lining apart in the cabin to access the nuts below and need 2 people to tighten them as a team. I would recommend unscrewing them if they are loose and cualking the holes then tighten them, chances are if they were loose they were letting some water in and you need to stop that before it is too late and you have some real damage on your hands. And deck screws or mounting bolts that do not tighten need attention and really should be resealed, this is something you should check once a year. Last spring my big project was to pull up all of my deck screws and recualk them all back in to prevent any rotting or water seepage, something many of us overlook or do not know to check.