Jet Ski Termanolgy, We are going to school you

​Advance curve: The amount the ignition advances as engine rpm increases.
Advanced timing: The setting of the ignition system to fire earlier, or faster, than set by the factory.
Aftermarket: The segment of the industry that manufactures replacement parts for stock watercraft (or putting groceries in your car).
Air/fuel mixture: The combination of air and fuel droplets that is ignited in an engine.
Amateur: A non-professional personal watercraft racer.
Amperage: The intensity or strength of an electrical current.
Ampere: The unit that amperage is measured in.
Ampere hour: A battery capacity rating.
Anneal: To heat metal and gradually cool it.
Axial flow: A jet pump that pushes the water out in line with the pump centerline. Guide vanes are used to straighten the flow of water from the impeller, and eliminate torque reaction which can cause the craft to roll during acceleration.
Base gasket: The gasket used to create an airtight seal between the cylinder and the crankcase.
Beginner: A rider or racer with little or no experience .
Bilge: The inside bottom of a craft's hull, and the water that collects there.
Bilge pump: A pump (either mechanical or electrical) to remove bilge water from the inside bottom of a craft's hull.
Blue book: A book that lists craft models by year and gives a range of current value for their condition.
Boarding platform: The area at the rear of a runabout or sport craft's deck, where a rider climbs on.
Bond line: The imaginary line around a craft where the hull and the deck are joined together 
Bond flange: The overlapping mating section where the deck and hull are joined together 
Bore:The internal diameter of a cylinder or hole .
Bow: The front or forward end of a personal watercraft.
Bow eye: The hole in a bow, used to secure a craft to a trailer, boat, or dock.
Bulkhead: A structural reinforcement built into a craft's hull.
Bumper: The plastic padding affixed to a bond flange to provide protection in small collisions (usually well-used on PWI Senior Editor Paul Carruthers' boats).
Buoy: An inflatable object used to mark a turn on a race course (or a young male child).
Butterfly: A disc-shaped valve within the throat or body of a carburetor.
Bypass: A fitting used to route water away from the cooling system to a visible location, to dry out the exhaust system and allow a visual inspection of the system's function 
Capacitor discharge ignition: A self-powered ignition which relies on the quick discharge of a capacitor to fire the spark plugs.
Carbon fiber: A lightweight material composed by adding resins to graphite cloth. Often used to build race hulls.
Carburetor: A device used to combine gas and air into an explosive vapor.
Carburetor throat: The main passage or bore of a carburetor.
Carburetor venturi: The hourglass-shaped center of certain carburetor throats.
Cast: To melt metal and then pour it into a mold.
Cavitation: A formation of cavities or pockets of air, which often occurs in the jet pump 
Center of gravity: The point in an object around which its weight is evenly balanced.
Chine: A longitudinal member lying along the bottom side of the hull 
Choke: A valve that is used to reduce the air supply to an engine during starting 
Circlip: A semi-circular retaining clip used to hold the wrist pin in a piston.
Clearance: The distance between two parts or surfaces.
Closed-course race: A competition in which entrants race several laps around a buoy-marked track.
Combustion chamber: The space in an engine where fuel is ignited and burned 
Compression: A reduction in the volume of gases within an engine's cylinder.
Connecting rod: The metal bar that connects the piston to the crankshaft.
Convergent cone: The rear, metal cone of an expansion chamber for a two-stroke exhaust system.
Coupler: A part or device used to connect the crankshaft to the driveline on a personal watercraft.
Course marshall: An on-water official who helps control the race and assists stopped riders on the course.
Crankcase: The metal case that forms the bottom section of an engine, housing the crankshaft 
Crankshaft or crank: The flywheel and shaft assembly of an engine.
Crankshaft axle: Either one of the two outer ends of a crankshaft.
Crankshaft flywheel: The heavy wheel that is attached to a crankshaft for balance.
Crankshaft journal: The bearing surface of a crank pin or crank axle.
Cylinder: The chamber in which the piston travels up and down in an engine.
Cylinder head: The upper part that is fitted on top of the cylinder, and houses the spark plugs.
Cylinder port: An opening in a cylinder.
Cylinder sleeve: The inner liner or section of a cylinder.
Damper or dampener: A rubber or urethrane device that deadens or stops shocks within the driveline coupler.
Deck: The upper structural body of a watercraft, located above the upper bond flange .
Decibel: A measurement of the relative intensity of noise or sounds.
Detonation: An improper type of explosion (usually caused by preignition) within the combustion chamber.
Divergent cone: The metal cone of a two-stroke engine exhaust system (also called the “diffuser cone”).
Dome: The spherical portion of a combustion chamber.
Drain plug: A device of various materials constructed to block the drainage of a compartment.
Drive shaft: A shaft that connects the engine to the jet pump.
Dry suit: A watertight, Michelin Man-like outfit worn when riding in extremely cold conditions.
Electrolyte: A solution that will conduct an electric current within a battery.
Engine block: The main part of an engine. It contains the cylinders.
Engine plate: What mounts the engine to the motor mounts.
Exhaust manifold: The waterjacketed portion of an exhaust system that connects the head pipe to the cylinder.
Exhaust pipe: A large-diameter metal tube used to carry exhaust gases, pressure waves and sound waves away from the exhaust manifold.
Exhaust port: The opening in an engine through which exhaust gases exit.
Exhaust valve: An electronically or mechanically controlled valve that adjusts the height of the exhaust port according to rpm or exhaust pressure.
Expansion chamber: A long, metal chamber in an exhaust system.
Factory: A watercraft manufacturer's headquarters.
Factory racer: A competitor that is directly sponsored by a manufacturer.
Factory race team: A squad of riders and technicians that is directly sponsored by a manufacturer.
Factory sponsor: A company that pays money or supplies product in order to be officially affiliated with a factory team.
Fiberglass: Fine, flexible filaments of glass. When combined with resin, it makes up the material used to manufacture some watercraft hulls.
Flame arrestor: An air cleaner that will not permit a flame to escape through its element.
Flywheel: A weighted wheel on the end of the crankshaft used to trigger the ignition system, and generate current for the battery. It also houses the ring gear used to start the engine .
Flywheel magneto: A system that utilizes magnets mounted to a flywheel to produce an electrical charge 
Footwell: On a runabout or sport craft, the platform area where the rider's feet go.
Forge: To form metal by heating it, and then hammering it into shape.
Freestyle: A competition in which entrants are judged during a two-minute routine of tricks and maneuvers.
Fuel filter: A device used to prevent dirt and foreign objects from passing through the fuel system.
Fuel injection: A method of pumping pressurized, vaporized fuel into internal-combustion engine cylinders.
Girdle kit: A set of studs that passes through the cylinder block, pulling the engine cases and the cylinder head together.
Gunwale: The vertical walls that surround the tray or footwells of a personal watercraft (or a very large rifle).
Handlepole: On a ski (standup craft), the pivoting arm that supports the handlebar.
Head gasket: The seal that is used to join the top of an engine cylinder and the bottom of a cylinder head.
Head pipe: The chamber (usually waterjacketed) that is directly connected to the exhaust manifold of an engine.
Homologation: The process of officially approving, confirming or allowing a component or watercraft to compete in IJSBA events.
Hull: The lower structural body of the watercraft located below (and including) the lower bond flange.
Idiot light: A warning light that goes on when something in the system goes wrong (low oil level, engine overheating, etc.) (also known as a Jonnum light).
Idle: The lower operating speed of an engine that is running.
Ignition: A mechanism or system used to provide and control the spark that ignites the fuel vapors within an engine.
Ignition coil: An induction coil that acts as a transformer in the ignition system by converting low-voltage electricity into high-voltage electricity.
Ignition timing: The speed and order in which the spark is provided to the cylinders to ignite the fuel/air mixture.
Ignitor: The control (brain) unit of a CD ignition system. Often referred to as the “black box”.
Impeller: A propeller that resides in a pump housing and creates thrust for a personal watercraft.
In-line twin: A two cylinder engine with its cylinders in a row.
Intake grate or scoop grate: A grill-like component that mounts on the bottom of a hull and feeds water to the jet pump while also preventing foreign objects from entering .
Intake manifold: The element of the intake system between the engine block or crankcase and the carburetor, which channels the air/fuel mixture between the two.
Intake port: An opening through which the air/fuel mixture is taken into an engine.
Intake stuffer: A funneling device that mounts in the intake tract to increase velocity .
Intake tract: The complete system of related parts and areas involved in taking the air/fuel mixture from the carburetor into the engine (or Hain's throat).
Jet pump or pump: The veined, cylindrical component which directs the flow of thrust created by the impeller.
Keel: The lower-most point along the centerline of a V-shaped hull .
Kill button: A button connected to a switch that stops the ignition.
Labyrinth seal: A two-stroke engine crankshaft seal with staggered grooves.
Lanyard: A short chord which connects from the rider to the kill button so that the engine will stop running in the event of a get off.
Life jacket or life vest: A buoyant device worn by the rider to provide flotation in the event of an emergency. Also referred to as a personal flotation device (PFD).
Liquid cooled: Cooled by a liquid such as coolant, water or oil.
Magneto: A system consisting of a small, electrical generator that uses a magnetic field to produce electrical current .
Mixed flow: A pump with an impeller in a tapered housing, where water flow has some incline to the impeller access. This adds centrifugal force to the water as it is pressurized by the water. The pump housing collects the pressurized water and directs it aft in a high-speed stream.
Moto: One of two or more races which are combined to determine an overall winner.
Motor mount: The rubber damper used to bolt the engine into the hull.
Musclecraft: A craft which uses a large-displacement engine.
Neoprene: A synthetic rubber used to make wetsuits.
Oil injection: An engine lubrication system that pumps oil from a reservoir into the intake manifold or carburetor.
Offshore: An endurance watercraft race which uses a long course.
Paddle throttle: A wide, trigger-like hand lever, mounted to the handlebar and operated by either the finger or the thumb, which actuates the carburetor butterfly valve.
Passenger: Someone on a watercraft in addition to the driver.
Performance runabout: A sporty, race-oriented runabout watercraft.
Personal watercraft: A vessel which uses an inboard motor powering a water jet pump as its primary source of motive power. It is designed to be operated by a person sitting, standing, or kneeling on the vessel rather than inside it.
Piston: An aluminum, cylindrical piece that moves up and down in the cylinder, providing compression..
Piston ring: A round, metal piece that fits in the groove around the upper part of the piston. It creates a tight fit between the piston and the cylinder wall, which makes internal compression the engine possible.
Port: The left-hand side of a craft, or an opening in an engine cylinder.
Premix: A gas/oil mixture which provides lubrication to internal engine components.
Pro: The highest category of personal watercraft racer.
Pump nozzle or nozzle: A cone-shaped device which attaches to the back of the jet pump and pressurizes the flow of water.
Qualifier or heat race: A preliminary race held to determine which riders will advance to the main event.
Race gas: High-octane fuel, formulated especially for high-compression, high-rpm racing engines.
Reed petal: A thin, fiber or metal plate that fits on a reed cage. The main component of a reed valve.
Reed valve: A valve used for fuel/air induction into certain two-stroke engines.
Reed stop: The metal portion on a reed block.
Reed stuffer: A wedge-shaped device that fits into the reed cage and increases the air/fuel velocity.
Resonator: A device in an exhaust system that uses reflection to mix sound waves and reduce the decibel level.
Retard curve: The amount the ignition retards as the engine rpm changes. 
Retard timing: To set the ignition timing so that the each spark plug fires later during the piston's travel upward on the compression stroke.
Rev limiter: A device which prevents the engine's rpm from going above a certain speed.
Ride plate: A flat piece of metal that covers the cut-out for the pump. The craft “rides” on this plate.
Ride tray or riding platform: On a stand-up craft, the platform where the rider's feet go.
Runabout or sit-down: A personal watercraft that is designed for one or more people and has a seat. According to IJSBA rules, it must weigh more than 340 pounds, be shorter than 126.0 inches, and have a hull width between 38.0 and 50.0 inches.
Sanction: An agreement between an organizing body and a promotor, that stipulates specific criteria to be met by the promotor in exchange for that body's support.
Seizure: The grasping or binding of something. Happens to certain internal engine parts, when overheated or lacking proper lubrication.
Sheet-molding compound: The material used for building the hulls of most watercraft. It is a combination of fiberglass mat and polyester resin.
Ski or stand-up: A personal watercraft that is designed for one person to stand on and is controlled from a pivoting handlepole. According to IJSBA rules, a ski must weigh more than 225 pounds, be shorter than 120.0 inches long and have a hull width between 20.0 and 30.0 inches.
Slalom: A watercraft competition in which entrants are clocked one at a time as they zig-zag through a buoy course.
Spark plug: A device used to ignite the air/fuel mixture within the combustion chamber.
Spark plug gap: The distance between the spark plug's center electrode and its side electrode.
Sponson A special planing surface which may be integrated or attached to the hull's sides or transom.
Sport: Personal watercraft which are designed for one or more people and have a seat. They can be ridden in either the sit-down or stand-up body position. According to IJSBA rules, a sport craft must be greater than 250 pounds, less than 120 inches long, and have a width between 26.0 and 38.0 inches.
Spring suit: A wetsuit that features short legs and short sleeves, for riding in hot weather.
Staging area: The area near the starting line where personal watercraft and their riders wait for their scheduled race.
Starboard: The righthand side of a personal watercraft.
Starter motor: An electric motor used for starting a watercraft engine.
Steering cable: The cable used to connect the steering system (handlebar) with the steering nozzle.
Steering nozzle: The portion of the pump which pivots left and right to control the direction of thrust and steer the watercraft.
Steering stem: The rotating shaft to which the handlebar mounts.
Stern: The rear, aft end of a personal watercraft.
Stinger: The small-diameter rear section of an expansion chamber.
Strake: A continuous ridge which extends along much of the length of a hull's bottom. It is used to improve tracking and cornering, as well as providing lift.
Tech inspector: The person who checks all competing watercraft for rule compliance and eligibility.
Three-seater: A sit-down runabout craft designed to carry three people.
Throttle: Any valve used to regulate the flow of air/fuel to an engine.
Throttle cable: The cable used to connect a throttle lever to the carburetor's throttle-valve linkage.
Thumb throttle: A throttle-actuating lever mounted on the handlebar and operated with the thumb.
Top loader: A type of intake grate that utilizes a wedge perpendicular to the grate's parallel bars, in order to scoop more water up into the top half of the pump. This loads the pump more evenly.
Total-loss ignition: A watercraft electrical system with no charging system to recover electricity. It receives its electrical supply from the battery, which must be charged periodically.
Tote: A balloon-tired cart used to transport watercraft short distances and across rugged terrain.
Traction mat: A thin, rubber material bonded to the footwells, ride tray or boarding platform of a watercraft.
Traction pad: A thick, rubber material bonded to the footwells, ride tray or boarding platform of a watercraft.
Transfer port: An opening in the engine cylinder of a two-stroke watercraft engine, used to transfer the air/fuel mixture from the crankcase to the combustion chamber.
Transom: The vertical, rear portion of the hull, which connects the sides and the bottom.
Trigger pickup: On a total-loss ignition, the magnet-activated mechanism which signals the ignition coil to fire.
Trigger throttle: A finger-actuated lever mounted to the handlebar and used to actuate the throttle valve.
Trim: The up-and-down movement of the pump nozzle, which can change the hull's attitude.
Triple cylinder: A watercraft engine with three cylinders.
Twin cylinder: A watercraft engine with two cylinders.
Two-seater: A sit-down runabout personal watercraft designed to carry two people.
Two-stroke engine: A watercraft engine that draws an air/fuel mixture into its crankcase for primary compression. This happens as the piston travels upward to compress the already-transferred air/fuel mixture. Secondary compression, ignition and power result. On the downward stroke, the exhaust port is open, followed by the opening of the transfer ports. This action transfers the mixture from the crankcase to the combustion chamber.
Velocity stack: A metal cylinder with a flare on its outer end, that is installed in the mouths of certain carburetors to make better use of air velocity.
Waterbox: The final portion of a watercraft exhaust system, which mixes water and sound waves to muffle the exhaust noise.
Waterjacket: A cavity and/or passage that allows liquid to pass in and around a designated area (for example, coolant in a watercraft engine circulates through a waterjacket).
Wetsuit: A neoprene rubber outfit worn when riding in cold conditions.
Wrist pin: The pin that allows the piston to pivot on the connecting rod.
A or a: Ampere(s) or amperage.
ABDC: After bottom dead center.
AC: Alternating current.
ACV: Alternating current voltage.
AH: Ampere hour(s).
APBA: American Power Boat Association.
ATDC: After top dead center.
Amp hr: Ampere hour(s).
BBDC: Before bottom dead center.
BDC: Bottom dead center.
BIA: Boating Industry Association.
BNG: Bold new graphics.
BTDC: Before top dead center.
cc: Cubic centimeter(s).
Carb: Carburetor.
CDI: Capacitor discharge ignition.
CG: Center of gravity.
dB: Decibel
DC: Direct current.
DCV: Direct current voltage.
DNR: Did not race.
DNQ: Did not qualify.
DNF: Did not finish.
DQ: Disqualified.
Dyno: Dynamometer.
ECU: Electronic control unit.
EPA: Environmental Protection Agency.
FRP: Fiberglass reinforced plastic.
fl oz: - Fluid ounce(s).
HIN: Hull identification number.
HP: Horsepower.
IJSBA: International Jet Sports Boating Association.
IMTEC: International Marine Trades Exhibit and Convention.
LCQ: Last chance qualifier.
mm: Millimeter.
mph: Miles per hour.
OE: Original equipment.
OEM: Original equipment manufacturer.
oz: Ounce(s).
PFD: Personal flotation device.
PSI: Pounds per square inch.
PWC: Personal watercraft.
PWI: Personal Watercraft Illustrated.
PWIA: Personal Watercraft Industry Association.
qt: Quart(s).
R/A: Runabout.
R&D;: Research and development.
rpm: Revolution(s) per minute.
SAE: Society of Automotive engineers.
SMC: Sheet-molded compound .
TDC: Top dead center.
V: Volt(s); voltage.
VE: Volumetric efficiency.
WFO: Wide #*&@$% open.
WFQ: World finals qualifier.