You will need a small hand-washing brush, sponge or two, some detail brushes to get into some cracks, a good degreaser safe paint, one paint is diluted to be sure, some engines to dress for hoses and surrounding areas that can be dressed. You will also need some plastic bags or plastic wrap and rubber bands great great (how to make a car engine under the hood) to cover the distributor or any other sensitive electrical. Do not use foil to cover the parts. Soap areas near the degreaser case is diverted to areas of painted surfaces or aluminum heads which can cause discoloration. Also, before you begin to realize that the bilge pump of the boat could go. Once you reach a certain level, a float switch will send the water flowing to the outside of the boat is usually raised to just below the rub rail. So you may want a bucket platform on the outside of the boat to catch anything that might spill out you can not catch.
Periodically, you will have to stop the progress of work to pump out with your shop vac. Especially in cases where you are working on water, the fines can be strong and do not want to pollute the water with oil, fat will be produced when cleaning a bilge. Use the minimum amount of water needed and you minimize the problems associated with cleaning the engine room and bilges on these boats. Set your pressure washer 1200-2000 PSI and 180 degrees and work in short bursts and accurate as possible, if you have no dirt to use, but if you can rent one that is a better idea.