Best stick with the 3800's. Boats can draw a lot of amps. You wouldn't get much ooomph or run time with 2000 Mah bats.
Those Duratrax were the first bats I had in my SV27. They are durable and good to start out with. I would recomend getting a charger that will charge Lipo's as well in case you want to make the switch.
The SV27 is a blast.
Have fun.
Joe