Mine will slow down also, while they are good performers there are limitations. I tube around 20 mph or so with a teen/adult, when cornering, trim down and accelerate to carry speed. If you pull wide open you have no choice but to be slowed down when turning, especially if it's a 180, it's slowing down. I had to change my driving style from the old glass v hull. Leave yourself some throttle for the turns.
Only a pooch in sharp turns. Usually trimmed at 3/4. I have it 38 gps on straight shot with two adults and almost full tank. I was reading somewhere that a 13 pitch prop is better for water sports but you sacrafice top end.
TejasNewbie - we went out again today and a buddy went with that had been out with me before and noticed a significant difference with it trimmed down. My oldest even asked me to slow it down when turning because it was hurting his arms trying to hold on during the sling shot
The truth is the ESP center toon adds substantial weight and has quite a bit of drag. It's worthy of far more engine than 150 hp. The fact that you're getting 38 mph means the engine height and prop is correct for general cruising. Dropping back to a 13 pitch prop would work better for water sports, but it'd cost you some top end speed.