Assuming you've tried adjusting the throttle trim and that's not the problem. I was thinking it sounded like a binding issue and with the extra resistance of the water it can't reach full power. I would check for any binding in the drive line. And yeah as far as the leak goes my brand new supervee 27 leaked like a siv from more than one place. So I took all the hardware off and siliconed up all the holes. Are youu sure it is leaking or is it coming in from the hatch from reversing and running the boat? I have a brushles cable driven mini-v that leaked through the hatch so I just taped the hatch even though the way the hatch fits it is kind of a pain in the but to get it sealed up. I sank mine twice and burnt up 2 stock esc's the first week before I put a BL motor and a waterproof esc in it. So I learned the hard way to tape the hatch. But the easy way out (and maybe the best) would be to exchange it if you can get whoever sold it to you to take it back. Due to the nature of this hobby that is sometimes not an easy task. Good luck!