DON"T USE A POWER WASHER!!!!!
Did ya hear that? There is no need for a power washer on a sailboat and you can ruin your teak trim -not to mention that you'll blow dirty water into your cabin through the gaps around the cabin openings. The high pressure water will blow the soft cellular wood from between the hard grain lines of your teak trim and you'll need tens of hours of sanding to restore it.
All you need to clean the dirtiest boat is a box of tri-sodium phosphate from the paint department at your home store, a long handled soft vehicle washing brush, and a bottle of bleach. Put 2 cups of TSP and a cup of bleach in a bucket of water, wet the boat with the garden hose, then swab on a dose of the cleaning solution and let it sit for a few minutes while you move on to a second section. Come back and swab the first section again and hose it off. You'll be down to perfectly clean, white fiberglass. No more black mold, no dirt, you'd be able to repaint if you you wanted to. (By the way, TSP sounds nasty, but all it is is the "phosphate" that used to be found in laundry detergent. They sell it at home stores for cleaning prior to repainting.)
You can clean the teak wood by spraying it with full strength bleach, letting it sit for a few minutes until you see a grayish white scum lifting up from the wood, then rubbing it with the same brush and cleaning solution you used on the boat. It'll remove the gray and when dry, will be ready to oil.
Please, save the pressure washer for your concrete driveway.
