Standard torque specifications based on fastener diameter may not apply here. Those standards assume the fastener is up against a metal casting or similar. With compressible materials like fiberglass and sealants under the fasteners Those torque values may be too high and may even damage (crush) the fiberglass. If the boat manufacturer has a suggested torque value for your particular application that would be useful. This is not to be compared with, say, torquing engine head bolts which is a much more exacting science.