Paul and Josh Gahr take Jack Bright's "Rock Chucker" for a spin
The boats are divided into three classes based on their allowable hardware. Here are the class definitions, straight from the USSBA rule book:
Super Modified Class:
Engine: Single domestic cast iron, normally aspirated, CID 367 cubic inch maximum. Maximum 2 valves per cylinder.
Crankshaft: Open
Rods: Open
Pistons: Open
Camshaft: Open
Heads: Stock valve angles and stock port locations. Example = Chevy valve angle 23 degrees. Ford valve angle 20 degrees. Chrysler valve angle 18 degrees.
Lifters-Rocker Arms: Open
Lubrication: Wet sump or Dry sump is allowed.
Intake Manifold: Open Induction: Single Carburetor only.
Exhaust: Any exhaust allowed. Must meet individual track requirments. Track owners will notify the USSBA of any specific noise requirements 1 month prior to any race.
Jet Drive: Single unit only. Direct drive only (no gearboxes) otherwise no restriction. A functional reverse system is required.
Fuel: Any 100 low lead or leaded racing fuel. No additives, oxygenization, Methanol, Nitrous Oxide, and Nitro Methane are allowed. Race organizer may control fuel.
International Group A (400) Class:
Purpose: This is the 1st of 2 classes recognized for international competition. The rules presented here are intended for USSBA sanctioned events and may not qualify for international competition.
Engine: Single cast iron only, CID 412 cubic inch maximum, 368 cubic inches minimum. Maximum 2 valves per cylinder, push rod operated, with a maximum of 8 cylinders. Internal combustion only.
Crankshaft: No titanium or alloy.
Rods: No titanium or alloy.
Pistons: Open
Camshaft: Single camshaft only.
Heads Cast iron only. No cutting or welding of heads other than crack repairs. Valve angles and location must be OEM stock only. Porting will be allowed. All port and bolt locations must be OEM stock. Minimum valve angle to the emgine block face is a follows: Chevy 23 degrees, intake port size template Felpro gasket P/N 1206, Ford 20 degrees intake port size template Felpro gasket P/N 1262, Chrysler 18 degrees intake port size template Mopar P/N DCC4120211
Lifters-Rocker Arms: Open
Lubrication: Wet sump or Dry sump is allowed.
Intake Manifold: Open
Induction: Single 4 barrel carburetor, square bore, with a maximum of 4 venturis. No fuel injection or electronic fuel metering device permitted. No additives may be discharged into the intake tract.
Ignition System: Open
Exhaust: Any exhaust allowed. Must meet individual track requirments. Track owners will notify the USSBA of any specific noise requirements 1 month prior to any race.
Jet Drive: Single unit only. Direct drive only (no gearboxes) otherwise no restriction. A functional reverse system is required.
Fuel: Any 100 low lead or leaded racing fuel. No additives, oxygenization, Methanol, Nitrous Oxide, and Nitro Methane are allowed. Race organizer may control fuel.
Super Boat Class:
Purpose: This is the 2nd of 2 classes recognized for international competition. The rules presented here are intended for USSBA sanctioned events and may not qualify for international competition.
Engine: Any engine minimum of 231 cid must be forced induction, 350 cid to 419 cid must be fuel injected ( mechanical only no OEM ) or must be multi carbureted running on methanol. All engines larger than 420 cid have no restrictions.
Exhaust: Any exhaust allowed. Must meet individual track requirments. Track owners will notify the USSBA of any specific noise requirements 1 month prior to any race.
Jet Drive: Single unit only. Direct drive only (no gearboxes) otherwise no restriction. A functional reverse system is required.
Fuel: Alcohol (methanol) fuel. Booster additives are not allowed. Any type gasoline allowed. Any boat using methanol must display a red “M” on each side of the boat. Letters must be at least 7 inches tall.
