I?ve got an American Express a.k.a. Henglong 3837 Atlantic boat that I?m trying to upgrade with new drive shafts and propellers. When I start out slow the boat moves ok but when I get past 1/2 throttle there is no pick up and it looks like the propellers are creating splash but not pushing water. It has a twin motor setup spinning in counter rotation with 3 blade 36mm propellers. These are the propellers I installed:

uxcell RC Boat Propeller 4mm... https://www.amazon.com/dp/B06XJ3SWSH...p_mob_ap_share

Not sure what?s wrong. Is this what cavitation is? It originally came with 2 blade propellers that worked fine but one broke. Should I just go back to 2 blade propellers?

I know these boats can go much faster there are YouTube videos of it on the internet:

https://m.youtube.com/watch?v=Jesq0AfZdoA
https://m.youtube.com/watch?v=vn22QfI3bjc

Totally new to RC boating so any help is appreciated. TIA!