As long as you don't hold the nozzle within an inch or two of the hull you should be fine. The farther you hold the nozzle from the hull the lower the pressure of the water impacting the hull is. only go as close as is needed to remove crud. Also pretty much all pressure washers come with a variety of nozzles that give different pressure sprays. Use the intermediate level nozzle and you will be OK. I use that one on my cars with no problems.