jboat73 - Since you are getting your boat directly from the manufacturer, I'd suggest you ask them for a recommendation about motor size. Describe where you're sailing.
Many of the boats that are being referenced here are pocket cruisers, which are much heavier than your Flying Scot. As Ulladh said, many use the Flying Scot without any motor at all, and keep a couple paddles for emergency. The one I rented had no motor, and we rented it on a dead day.
I see some guys talking about getting a motor with an alternator to charge your battery, etc. They definitely don't understand your boat. You'll need to filter some of the recommendations based on how well you think the posters understand your boat and sailing range.
For what it's worth, I think it's likely that 2 hp is enough to get you wherever you will need to go, even against the Delaware's tidal current. It's a small boat with very little draft. Most of the guys recommending 4-6 hp are sailing much heavier boats than yours.
The capacity plate says 4 HP, but that's the maximum. (And I question whether you need this much.) For this reason, I wouldn't go over 4 HP, even if the 6 HP motor is a "twin." If you ever get pulled over by law enforcement, you may get some tough questioning about exceeding the boat's rated capacity. And the rating is about more than just dead weight - it's about what can go wrong if you accidentally throttle up too high (like swamping the boat).
Light weight is a benefit for boat trim, even if you don't care about removing the motor every time. Since it's off-center, you want to minimize the boat's list, especially since you're keeping it in a slip. And if it ever needs service, you'll be glad you have lighter weight so you can pull the motor instead of the whole boat.
I read somewhere the Suzuki makes the lightest 2.5 hp motor. I've seen online specials for under $700:
2012 SUZUKI 2.5HP OUTBOARD MOTOR
Suzuki Outboards 2.5 Horsepower
But if you're going to buy in this size range, I'd consider an extra $140 for the air cooled 2 hp Honda. Actually its weight looks exactly the same as the Suzuki. Note that Honda has 2 shaft lengths in this size, and you should probably get the longer shaft:
Honda BF2DKLCH Outboard Motor (Four Stroke) - Price: $838.08
One critical thing to look at is how whatever motor you pick can be locked to the transom. This is critically important if you're keeping it in a slip, especially if you're considering downtown Philly.