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Traxxas "Titan" 14.4 Volt motor, 23 turn single. This is the same type motor(s) used on the Traxxas E-Maxx trucks. The 20" hull is a so-so RS (Radio Shack) shallow vee hull.
I'm still experimenting with cheap hulls that I can find. I run this boat on 8 sub C cells or 9.6Volts. Stock power was 6 sub C cells or 7.2 Volts.
Boat is still slow by racing standards . Got a top speed of only 13.9 MPH using a
Garmin etrex GPS I taped on top of the boats hull. This is a little better that the 5.8 MPH stock speed of the boat.

The motor you see on the left was the RS 540SH, 6 Volt, 23 turn single motor that was originally used on that boat. The Motor on the right is the "monster" Traxxas Titan 14.4 Volts, 23 turn single motor.

GulfstreamI