Originally Posted by SchockT
I use a pressure washer on my boat, but it is not a high pressure gas unit that could take your fingers off, it is a little Karcher electric unit. It does a great job of taking a winter's worth of green slime off the decks. I am very careful not to direct it at deck fittings where there is a danger I could force water under them, although I doubt it could do any harm to properly bedded fittings. I just use it for the larger surfaces, and then I go at the nooks and crannies with brushes.
I do EXACTLY the same thing, with a Karcher also. The small electric pressure washer does wonders at getting that black stuff (mildew?) off of the decks. I've scrubbed and scrubbed that stuff with various brushes and it will not come off even with deck cleaners that contain bleach. One pass with the pressure washer and it's gone. I really doubt that water can be forced through 3 layers of FRP and a layer of gelcoat. It -might- penetrate your skin if you spray your foot with it; so watch your toes if you are barefoot! If your deck leaks at the fittings; they are not bedded properly and any water on the deck will go through via capillary action (no pressure required).