As far as faster.....
Just go over the entire drive. My Sportster was running in the high 40's with one person on board... and it would cruse at 35 mph with 4 people, and the top up. (full speed, full load was about 40~42 mph)
SO....
1) Is you engine making full power? Full RPM?
2) is the impeller in good shape?
3) is the pump tight?
4) is there any leaks in the pump? (around the shoe, pump, carbon seal)
Finally... if you want good pulling power... a skat-trak "Swirl" impeller is your best bet. I ran one degree higher pitch than recommended, and bored my pump 1mm.
I remember... before selling my little boat... I was pulling my nephew on a wake board... and I think we were overweight. I'm 235, my brother is around 300... and my nephew, and his buddy were typical teen's. (around 140 each) I didn't have too many issues getting him up with my sportster.