Boat covers and tarpaulins
This category holds boat covers, outboard motor covers and with them straps, bungee cords and support poles. The size is chosen by hull length and maximum beam, and on top of that by the shape of the bottom. The vents are not a needless extra, because without them moisture stays under a waterproof cover and mildew sets in. And a support pole lifts the centre so that water does not stand on the cover, which in the end tears it open.
Boat covers and tarpaulins
This category holds covers for the whole boat, outboard motor covers and with them straps, bungee cords and support poles. A cover has two jobs, namely to keep water and sun out and not to keep moisture in, and it is the second one that gets underrated more often. The material is usually coated polyester, stated in deniers, as a rule from two hundred and ten to nine hundred. A higher number means a coarser and tougher fabric, but also more weight and a bulkier folded size.
The first thing is the size by hull length and beam. Covers are sold in length ranges and carry on top of that the maximum beam they take in, so you need both numbers. What counts in the range is the length of the hull and not the length with the motor or with the trailer, and that is exactly the most common mistake when ordering. The shape of the bottom counts as well, so a cover for a V-hull sits neither on a flat bottom nor on the floats of a pontoon.
The second is the ventilation against condensation. A fully waterproof cover with no openings turns the boat into a greenhouse in which water evaporates out of the bilge and settles on the inside of the fabric. That is why covers carry stiffened vents at the stern, which let air out but do not let water in. Without them moisture stays under the cover and mildew sets in on the upholstery and in the corners, even if it is not raining from above.
The third is the support pole against the puddle. Water standing on the cover stretches it, wears it through at the seams and in the end tears it open, because a hundred litres weigh a hundred kilos. A telescopic pole placed under the cover lifts the centre so that the water runs off to the sides. At the top it carries a mushroom-shaped head so that it does not push through the fabric, and at the bottom a foot so that it does not sink in itself.
The last one is the outboard motor cover, which is chosen by power. It is sold in horsepower ranges, because the size of the cowling grows with the power, so a single cover takes in a wide band. The choice is then between the cover over the cowling alone, which stays in place even under way, and the cover over the whole motor, which comes off before setting out.