Which Lake do you go to? I'm out at Jordan and a month ago I saw a speedster that looked like yours. Didn't want to pull up next to it and scare someone, but if that was you, great boat!
As far as top speed, I have a neighbor with an '04 speedster 200 310hp. He is a very tech savvy guy and knows his boat. I think he got a GPS speed in the 50+ mph. I have the 210 challenger with twin 215hp and I top out at 54mph. If I remember correctly, my boat is about ~1,000lb heavier so power to weight ratio, it would make sense for a 310 speedster 200 to have a top speed in the mid 50's. Has a lower profile, lighter weight, likely less air and water drag, so with 310hp, really expecting 50's.
I do remember my neighbor saying if it was just him and his wife, they'd get that. But if you have additional weight and people, you will probably see a drop in top speed in the mid 40's. That was the reason I didn't get a speedster and got a challenger with twin SC engines. The SC versions give you a more aggressive impeller pitch with the power and thanks to the boost from the SC, get more torque, like a turbo or super charged engine in a car. And with the higher seating capacity in the challenger, I can really feel power come in handy when I have 10 people and gear on board. Hole shot is overall slower, but thanks to the torque, I go from a top speed of 54mph with just me in it to around 48-50mph with 10 people. Acceleration is definitely slower, but maintaining higher speed helps a lot. With a NA aspirated, they're definitely GREAT for lower maintenance and fuel, but you do feel a drop in performance with extra weight and will see it in a more relatively significant drop in top speed, along with acceleration. Best way to visualize that is a car with RWD vs AWD in the rain. Both cars can be identical in make and model, as well as horsepower, but an AWD system helps put down that power more efficiently. Or, if you look at a honda accord vs BMW 328i, the accord makes 250hp, nearly the same as 328i. Both are sedans with similar weight and RWD. Reason why the BMW would be faster off the line is because unlike the honda that is a NA V6, the 328i is a I4 with a turbo. Thanks to that turbo, it makes more torque sooner in the RPM range and increases, while also having an overall higher torque. HP is the same, but torque isn't.
Other factors are involved, but more boost means more torque. And for boats, more boost allows for more aggressively pitched impellers that really help with hole shot, acceleration, and top speed, depending upon how its configured. NA engines can't go too hard without getting bogged down.
I may be wrong, so please correct me if I am. My experience comes from previously having a Yamaha AR190 with a single NA 4cyl 1.8L 180hp engine. Thing topped out at 43 but the moment you added more people in weight, performance dropped DRASTICALLY! Even with one person on board, and me trying to slalom ski (190lbs), The boat struggled really hard trying to accelerate and get up to speed. Having 2 NA engines really does help out a lot with pushing out higher volumes of water at lower speeds, even with the same power. Drove a friends Yamaha 210sx with 220hp. little bigger than mine, but similar power to weight. His could easily handle multiple people and skiing just fine. But when you add 10, you felt it suffer.