Radio Control Boats

The best car motors can be the worst boat motors
In our club we have tested a lot of different motors and found only very few car motors work in boats.
Motors designed for marine and airplane applications appear to be the best bet.

Motor selection is based on all the components of the boat: Hull shape, size & weight Geared or direct drive Voltage - speed control method Prop size/pitch. Each one impacts the performance of the other. First the Hull shape, size & weight will get you in the ballpark, smaller light weight boats can perform with higher RPM less torque motors in a direct drive, as you go larger you have to drop RPM for more torque or add gearing. Gearing is for torque, the average electric motor is a balance between rpm and torque, higher the rpm - less torque and vise versa. For example, 20K rpm free turn motor (no resistance), when installed the RPM could drop to 10K or more depending the amount of resistance, the motor will work hard to achieve the 20K pulling more amps which increases heat to the motor, wires, speed control and batteries, with a 2:1 gear ratio, the motor shaft turns at 20K and the gear shaft will turn at 10K the torque is decreased from the motor by a significant amount and the output shaft retains it, kind of like a block and pulley system, the RPM will drop, but most likely at a higher or same rate than without it and the motor does not have to work as hard keeping cooler and longer run time. Voltage, adding more cells for more power or longer running time adds weight which changes the weight component, one of the other components will need to be altered to compensate. Props have a major difference in performance and have to be selected (size/pitch) to the combination of all the other components. If your boat is not performing well, try different sizes and pitches before changing other components, it's the easiest and cheapest one. Most electric motors are the same diameter and only very a little in length, the term 500 can size does not mean it is a 500, the 550, 600 and motors made by Great Planes or Kyosho who have selections in RPM/Torque are still basically the same size. The Graupner motor series "can size" is roughly identified by the number, 300 & 400 are smaller, 500 and 600 are the same size, 700, 720 and 800 are larger.
Great Planes TwinLine Drive System Designed for the Great Planes Stinger SS and Wildcat SS Boats SPECS: Motors are the T-600 with one having an extended shaft out rear of motor - See specs below Load RPM's will be higher with inline configuration. The advantage to inline verses parallel is the torque plus RPM. The power delivery must be wired in series to get the performance they were designed for, sending 7.2v is half speed and 14.4v is full. See Controls & Wiring Both motors have the rear extended shaft, they can be pair with another motor to make two sets. Boat this motor is in: Graupner Electro Vee, GP Stinger (old) & GP Stinger (New)
Great Planes S-600 7.2-8.4 Volt Ferrite Motor Former Goldfire Motor 05 (550) Windings: 19 turns of .80mm wire. Timing: + 3 degrees Resistance: .37 ohms No Load 7.2V - 19,140 RPM 8.4V - 21,960 RPM Shaft Diameter: 3.17mm (.126") Free Shaft Length: 10.2mm (.408") Case Diameter: 37.0mm (1.48") w/flux ring 35.5mm (1.42") w/o ring Case Length: 56.8mm (2.27") 550 size can Weight: 215g (7.5 oz) Bronze bushings Closed end bell Epoxied balanced rotor Flux ring for increased power Boat this motor is in: Kyosho WaveChopper
Great Planes T-600 7.2-9.6 Volt Ferrite Motor Former Thrustmaster Motor 05 (550) size) Windings: 22 turns of .75mm wire. Timing: + 3 degrees Resistance: .52 ohms No Load 7.2V - 15,360 RPM 8.4V - 17,850 RPM Physical dimensions same as the S-600 Boat this motor is in: Lindberg PT Boat
Kyosho Aquaspeed Marine Stock SPECS: Voltage: 8.4V Current: 3.2A w/Load: 26,000 RPM w/o Load: 30,500 RPM Motor Length: 2-3/4" (To end of Shaft) Turns: 18 Torque: 500g-cm Best Choice Boat this motor is in: Kellogg's & Villain IV
Kyosho Dolphin Outboard II Powered by a 6-7 Cell Battery Motor is a Closed Endbell 550 type with Capacitor Pre-Installed and Flux Ring. Comes with Two 2-Bladed Propellers which are red (KYOB7000) (D42XP1.2 size). Lower End Unit is Black Plastic. Motor Cover is a Hard Black Plastic and is Already Mounted. Adjustable Transom Mount. INCLUDES: One RS-550SH Motor One Black Plastic Motor Cover with Decals One Hardware Set: Joint, Shaft, Frame Set, Screws, Nuts, Washers and Props. SPECS: Length: 5.5" Width: 3.1 Height: 8.1" Weight: .9 Lbs Suitable for any boat that needs an outboard electric motor Boat this motor is on: Taylor's Blade

SPEED 600 7.2 SPECS: 7.2 - 8.4 Volts w/o Load: 21,000 RPM Boat this motor is in: Graupner Mambo
SPEED 700 BB TURBO 9.6V SPECS: 8.4 - 14 Volts w/o Load: 15,000 RPM Runs best on two 7.2 six cell batteries run in series, sending 14.4 volts to the motor. See Controls & Wiring Boat this motor is in: Krick Mach 1 & Graupner Systems
GTX-600 Speedline Outboard Motor SPECS: Speed 600 motor 6” high, 12 oz. Stainless drive shaft, bronze gears 5 degrees tilt up and down Approx. 25 Amps current with a 7 cell nicad pack Not impressed with performance at this time, motor is heavy and requires batteries to be located as far forward as possible.
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