Use One All the Time
A pressure washer is one of the best tools in the cleaning equipment arsenal. I've used a Karcher 1250-psi unit since around 1995 with excellent success. It's great on any cracks (aluminum toe rail to gel coat, around the chain plate, Genoa track, etc.) and on the non-skid deck.In addition to the areas where you said you'd stay away from I'd add teak (it'll blast the soft grain out). Unless your chain locker has been made leak proof (chain locker pan to underside of deck) I wouldn't blast that area either because the splatter will drain into the V-berth.Avoid using early in the morning because they are a bit noisy and if there are neighbors or liveaboards nearby they probably wouldn't appreciate it.With regard to pressure, every one I've seen is adjustable so a high-pressure unit can be adjusted. Additionally, the distance of the wand from the surface can be varied.I've never had a gel-coat problem from pressure.