ORIGINAL: Mikeup

U-joint, i'd forget them too! I would go 3S lipo 4500maH and a 34mm prop in the 4 pitch. Your 3S at 2900 gives you 32,000 rpm and with a 34mm prop , i would backcut prop. Reason for backcut is to let motor wind out and lets boat go faster and less heat. Solid coupler to a .130 cable which is inside the shaft....... I have a 22'' mono like yours with a Leopard 2550kv but have a 34mm prop backcut on 3S and it is fast. 2550 x 11.1 = 28305rpm. Now if i would have put a 3000kv motor in, it would be unstable. I would have prop down to a 632 or a cnc 1.7- 32mm which wouldn't lift the rear end to much. I think a 5 pitch on a 34mm prop would be it. I think you'll like that size of boat. I just noticed it is a step model. My boat isn't a step model which in my opinion does turn well . I see a video where a 650 was bouncing ALOT and had a 1.4-36mm 3 blade prop which increased speed where a 2 blade 34mm prop would settle the 650 down enough to be stable for a stepped model, my opinion! The kv on the video was 4122 kv on 2S which is spot on. The 3 blade prop does make boat faster as i have a 29'' mono from BBY which has a 440/3 and a Villian 30'' with a carbon fiber 440/3 prop and gets to unstable with the 3 blade prop. Enough out of me, i think as i type, am retired.