Boy, I didn't think Grady was even making boats way back then! I guess they're an older company than I thought.
Do you have a livewell? You could T into that line. For the odd and short times that you'd use the washdown, that would suffice. Otherwise... there are some battery powered, portable washdowns on the market you could use - you toss the motor head into the water. Got some pics of your bilge space and access? If you haven't worked much on boats before, get used to the cramped conditions, especially on small boats... it's kinda the "name of the game" with most boats.