Boat registration numbers and letters stickers. Your boat will be allocated the required registration symbols you need to display upon registering your boat. These must be clearly visible in plain characters in a contrasting colour to the hull of the boat. The size of the symbol depends on the type of boat and must be able to be read from a distance of 30 metres. Vessels capable of planing must have symbols a miniumum of 150mm high on both sides. Personal watercraft registration symbols must be displayed on both sides at least 100mm high and easily seen while the craft is underway.