Riverhound: I own a 19' Eliminator Daytona with a 2.4L Mercury Bridgeport. As far as driving/docking, Outboards are much easier than V-Drives or Jets. They are extremely maneuverable and user friendly. At WOT, outboard tunnels will vary. A mirage with a 2.5 HI-PO is going to be a handful, but then again that boat will run 110MPH give or take. The 21' Elim Tunnel will be very stable and easy to drive well into the 90 MPH range.
As far as performance goes, if the motor is truly a 200 Pro Max and not a 225 Pro Max, it is my opinion that the boat is under powered. Even with a 225, the boat is under powered, but the 225 is easy to hop up. I believe the 21' hull needs the hi performance 260hp outboard or better yet, the newer 280hp 2.5 or 300 Pro Max. With 200hp, you can expect speeds of roughly 70mph - 75mph.
Reliability . . . all of the Merc's are reliable . . that is my experience. I have a mildly built bridgeport that puts out about 250hp and I have had ZERO problems. As far as regular maintenance . . annually, replace the water/fuel separater filter, lube in the gearcase, water impeller, spark plugs, and every once in a while, you may want to decarbon the motor. Other than that, there isn't much to do.
A few things to keep in mind from my 10+ years of experience in hot rod outboard tunnels. The closer to the surface you run your prop, the more strain you put on your gearcase. Outboard Tunnels operate best with the prop at the surface, therefore make sure your gearcase is stout or else you will end up losing a bearing, propshaft, etc. and it could cost anywhere up to $3,500 - $4,000 for a new one. You need a high perf. bearing carrier, and I would run a one piece shaft. Bob's machine shop out of Florida does excellent work. I run one of thier nosecones/low water pickup and bearing carrier as well as a Merc. one piece shaft.
If you run a jack plate, make sure to have a low water pickup and a water pressure gauge. I have been told to never run the water pressure below 10lbs. I run mine at 10 - 12 lbs. I have had no problems. At 5 lbs, I fried a motor. If you are going to run hard quite a bit, look into removing the thermostats from your motor and replacing with stainless washers. This will allow more water flow and a cooler running motor.
Last but not least, frequently check all the bolts that connect the motor bracket to the boat, and the motor to the bracket. With all the vibration, these tend to wiggle loose over time. Also run a transom saver while towing. This mounts to the trailer and runs to your motor providing support while on the road.
My $.02 would be to find a 21' with a 2.5 EFI 260hp or 280hp. I think you will kick yourself if buy one with less power. With 280 hp you should see 90+mph.
Good Luck! http://free.***boat.net/ubb/cool.gif