I know it would be a long ride but check out Don's Marine in Tiverton. He has Yamaha and Evinrude and is by far the best dealer I have ever done buissnes with. He will get the work done fast and stand behind it. All the workers there have always treated me as if I was customer number 1 and have been told this by everyone that I send there.
I don't own an outboard of any flavor, but the guys I know that do like the service at Stone Cove at the top of the freat salt pond. Their Mechanic, Brian, is supposed to be pretty good. I don't know if they are authorized ny anyone.
Me.......and since I keep my boat running pretty good, my freinds sucker me into keeping theirs running too but that's why I love 'em, they're my buds....and they bring the rum for later.