The tanks will will permeate a little bit and let some of the odors out. There is a coast guard spec on the permeation and all our tanks are within these specs. It is generally strongest in the port side rod locker because there is an open channel that runs straight from the tank to the rod locker. Not saying you shouldnt cover your bases to make sure there is not another more serious issue here, but the odor in the port rod locker is not uncommon. You can leave that lid open from time to time to let some of the odor dissipate. BCB