My boat (Lowe 2070 CC) is very similar, if not almost identical to the Cresliner. I love the boat and its utility. The CC design works well, but then again the wide beam allows plenty of room to walk around it.
I run right at 50 mph, with just me, 20 gal of gas and 3 batts. 45 mph with 4 people. Thats with a 115 Merc Opti 2 stroke.
Yamaha had some troubles with their 115s a while back. I think it was the 4 strokes but you may want to do some research on the motor.