RedactedNarrative: Operator #1 got WC #1 in morning on 9/11/2021 and had battery issues 2 weeks prior. At 1330 hours the boat was headed south in the river channel. There were no issues when it came out of the No Wake area. Operator got the boat on plane and noticed an issue with the starboard motor, he couldn't get it over 2800 RPM (normal RPM is 3100 coming up on plane). Operator backed off the throttle, checked to see if anything was plugged and noticed nothing. Operator tried coming up on plane and had the same issue a second time and noticed now the port motor had died. Passenger on board smelled smoke, and Operator then saw black smoke coming from the back of the boat. Operator killed both motors and opened engine compartment to see black smoke and visible flames. Operator got everyone away and had passengers put on life jackets. Operator used a fire extinguisher to put out the flame. Operator mentioned that all three batteries were changed prior to the voyage. The operator noticed a battery cable was resting on serpentine belt on the starboard motor. Operator believes the cause of the fire was from a possible electrical arc. There were no injuries and alcohol was not a factor.