Adding A Raw water Wash Down

[Stillrunning]

I'm looking to add a raw water wash down and I really do not know much about what to look for when purchasing. I have a 1983 CC and have room under the splash well to the left of the batteries. I know to use a brass pickup and a brass shut off valve but not sure what size pump to purchase to get the desired water preasure. The pump will be located close to the thru hull pick up and I do know that I need one thats self priming. Any ideas and thoughts would help and also I need to know who would have the best prices for ordering this stuff. Thanks for any help.