A good motor for the MERV? What is your budget? If the budget isn't an issue then have a look at NEU 1112 (I think it just fits with a little bit of modding) or 1110 (direct fit) series have to offer. If you are on a budget then a ARC 28-47-1 is a good motor too. The 4250kV is a little higher than stock but it is a very good little efficient motor. On 4S it was way cooler than the VXL motor on 3S it has to be a pretty efficient motor.

As for the ESC I used a Quark Roadster 65A (6S capable) which I used for speed runs but for running in the wet I used a Hobbywing EZRUN 60A that I waterproofed with plastidip. Worked a treat but I never actually drove through deep water but instead just puddles.