There are usually three types of construction for boat trailers. Painted steel, galvanized steel and aluminium. For traditional v bottom boats, there are two types of support mechanisms, rug bunks and rollers.
In our area where there are salt water and salt air, we are not in favour of painted boat trailers. Aluminium trailers flex a lot and there have been instances where some metal brackets have fatigued because of the flexing. Our personal favourite and the only trailers we use for our deliveries are the galvanized steel models. As for a support mechanism we prefer the rollers over the rug bunks. With rug bunks, it is extremely difficult to winch the boat onto the trailer. Rug bunks were designed for the boat to be floated off and on the trailer. However, if you have a shallow ramp or low tide it is sometimes not possible to launch or retrieve your boat. With a roller trailer, you do not have this problem and can launch and retrieve on almost any ramp. Support on a rug bunk trailer puts the total weight on only two bunks. On a roller trailer you generally only have about 100 lbs. on each roller, so it dissipates the weight of the boat over a greater number of contact points. This is why you can easily winch a boat onto a roller trailer. So, our suggestion and the only trailers we use to deliver our boats is the galvanized roller trailer. But we have given you the pros and cons so you can make your own decision.
Selection of the correct model trailer requires you to match your boat in two ways. First is the overall length and the second is carrying capacity. Length is easy. For carrying capacity, you need to add the weight of the boat, motor, full tank of gas, batteries and any other items that you traditionally carry in the boat. Now you are ready to select the correct model trailer.
Next, you have to be careful of the trailer manufacturers ratings. Some dealers might try to use the G.V.W.R. rating to show you the trailer has the proper capacity for your boat. But that would be incorrect. The G.V.W.R. (gross vehicle weight rating) is the total weight a trailer is rated to carry, but the carrying capacity is the G.V.W.R. minus the weight of the trailer. EXAMPLE: If the G.V.W.R. is 6,000 lbs. and the weight of the trailer itself is 1,200 lbs. you would be buying a 4800 lb. trailer. So, make sure the carrying weight of the trailer you are buying, not the G.V.W.R., is correct for your boat.