Geoff,
not sure on your entire setup but if your taking 200ltrs of fuel I'd say that 540kg all up is going to be light, once you add hull / motor etc.
My winch is rated 900kg, boat / motor full of fuel weighs under 700kg it works fine, but certainly works hard.
I ignored the rolling weight factor, and worked it out on the basic weight as if lifted, if you do that then any relief from a rolling load builds in a greater safety factor.
Ron