The boat came with 4 blade13x19 props but it only maxed at 4400 RPMs at WOT, so I got some 4 blade 13.5x15s and it does max out at 5000RPM now. If I run one engine though after 3000RPM it revs up like it's slipping and the boat doesn't pick up speed, both motors do it, just revs up to max really...