I have seen a number of folks go to great lengths to bring their Johnson Motors to Sunset Marine, Don Heath in Hamptons. I hear good things about him and that he is very honest, but don't have any personal experience to share.
I suggest Sports Marine on RT 17. I have always had a Johnson and have had them serviced there. I personally have had no complaints. Respectable prices and generally finish when they tell me they're going to finish. Ask for Don. Good luck.
Highly rec Newport Marine 12670 McManus Blvd in Newport News. These guys have been the only ones to touch my 200 Johnson since I bought it new in 1991, still running strong and they stand behind their work. 757-877-7466
I have used both Sports Marine and Sunset Marine in Hampton before and Sports is the way to go no question. If you use Sunset Marine you will be lucky to get your boat fixed by Valentines Day, despite what they will tell you initially.