I have used a pressure washer to get algae off of a pool.
slows the jet down so much that you have to be very, very close for it to work
, so you would be cleaning
a very small section, and since your holding it so close, itís likely to damage your paint
Then there is the issue of holding a reaction jet in Your hand, so staying next to the Boat is going to be tough.
So easy to just wipe the boat down once a month so no scraping is required, if your scraping regularly, likely you need a new bottom.