RedactedNarrative: Operator stated they backed V1 into the water and turned on the blowers for 3 to 5 minutes prior to starting the engine. He started the engine and it died once. He then choked it and tried to start it again. At that time he heard an explosion under the engine cover and noticed smoke and flames. He attempted to use a fire extinguisher but it was not operational.  He abandoned V1 and it burned to the waterline destroying everything.  It was determined the carburetor was faulty and caused the fire.