If you are in the US go to WestMarine, they have a Spray...i think its boric acid...not sure.... it stinks like hell but you spray it on leave it about 30min (in shade) and then us a Karcher or similar Powerwasher and it goes of pretty good. i have now Bottompaint so dont remember the Name but go to WestMarine they know how its called, AND WEAR GLOVES!!! I didnt and even 4years later i remember the pain that night ....
I'd certainly try using a power washer. On my old boat though, I would be careful around the rivets. Some are loose as it is.
If you are in the US go to WestMarine, they have a Spray...i think its boric acid...not sure.... it stinks like hell but you spray it on leave it about 30min (in shade) and then us a Karcher or similar Powerwasher and it goes of pretty good. i have now Bottompaint so dont remember the Name but go to WestMarine they know how its called, AND WEAR GLOVES!!! I didnt and even 4years later i remember the pain that night ....