Eh, I don't know about the intake becoming clogged. I had, over the summer, a Sea Sprite 23 with a 5hp Evinrude (REAL old one) and I would routinely leave it for a month or so when I was moving it up the Hudson and through the Erie Canal. I never had a problem with overheating until I screwed up the oil mixture and toasted the engine. It's amazing how fast that can happen! I left the boat for six weeks in brackish water in Newburgh, NY and when I came back to it, the thing started right up and chugged along for another 200 or so miles. I did have to clean the prop and lower unit but the intake wasn't clogged and she pumped water fine. It's possible that you might get more growth in the Chesapeake but the conditions seem similar to me. I dunno, I'd definitely get more opinions before you sell the boat. And certainly don't take mine as the gospel truth!

Out of curiosity, do you own an Ariel or a Commander? I know there was an Ariel in the DC area with a Seahorse Outboard that was for sale last spring. Red hull. Is she now yours?