I have a 2006 f150 Yamaha 4 stroke and during the last service I noticed salt building up on the motor under the cowling. Is it ok to rise down the motor with the cowling removed.
I would think that so long as you don't get carried away with the hose, you should be OK.
Might want to get some Salt Away to assist your efforts. http://www.saltawayproducts.com/Products.htm
Once you are done, dry everything off as best you can and allow the sun and breeze to do its work.