Lightweight, liquid-cooled, DOHC 16-valve 1235cc dry-sump four-cylinder engine features a one-piece upper-crankcase/cylinder block engineered to withstand the rigors of marine duty. The inherently efficient, low-emissions four-stroke design consumes less fuel than a comparable two-stroke engine and meets all current CARB and Environmental Protection Agency (EPA) emissions standards.
Class-leading performance is provided by a water-cooled IHI(r) turbocharger with water-cooled intercooler. The AquaTrax(tm) turbocharger produces a maximum boost of 13 psi to generate 32 percent more power than a normally aspirated engine. The turbine bearing is an enclosed, ceramic-ball design that withstands sustained high-rpm compressor operation while providing nearly vibration- and friction-free performance. Water cooling of the turbocharger housing maintains optimum turbine operating efficiency, while the water-cooled intercooler assures a denser intake charge to provide maximum power and combustion efficiency. An electronic control unit (ECU) monitors atmospheric pressure, boost pressure, engine speed, oil and water temperature, intake air temperature and an engine knock sensor to manage an electronic waste gate valve that controls turbocharger boost, protecting vital engine components and maintaining long engine life.
Side-mounted cam chain and ultra-narrow cylinder-sleeve spacing reduce engine size and weight.
Crankshaft main bearings feature a micro-grooved bearing surface to improve oil retention and bearing durability as lateral loading occurs throughout a broad range of operating conditions.
DOHC-actuated valves use a simple, lightweight and direct cam-over-bucket design.
Four-valve cylinder head design with a narrow, 30-degree included valve angle creates a compact combustion chamber for optimum efficiency and power output at all rpm levels.
Silent-type cam chain reduces engine noise, while an automatic chain tensioner virtually eliminates maintenance.
Idle screw adjustment conveniently located on front side of engine for ease of adjustment.
Unique gear-driven dual engine-balancer system virtually eliminates high-frequency engine vibration.
Oil jets located on the crankcase main journal castings continually cool piston undersides, ensuring consistent operating temperatures and even better engine life under maximum power.
Forged pistons and connecting rods are designed to withstand the rigors of turbocharging. The top piston ring land is anodized, and a chrome-plated top ring further enhances durability.
Honda Ignition Control System (ICS) protects the engine from abnormal operating conditions.
Air intake system features an intake port mounted centrally in the hull and a labyrinth airbox construction with paper air filter. Together they keep water out of the engine during normal operation and if the craft is accidentally overturned.
High-pressure programmed fuel injection (PGM-FI) delivers fuel at 43 psi to four injectors, each mounted in a 38mm throttle body. Fuel is delivered through four laser-drilled nozzle holes in each injector, producing a highly combustible air/fuel charge for maximum combustion efficiency and power.
The ECU provides two digital 3-D fuel injection maps for each cylinder, creating the ideal fuel mixture and spark advance settings. A sophisticated throttle sensor and advanced fuel injection mapping combine to produce smooth and linear throttle response, responding precisely to minor throttle and waste gate adjustments to maximize driveability, acceleration and drive pump performance.
A unique fast-idling system uses an electric stepping motor to maintain a stable idle speed when the engine is cold. An automatic fuel-enriching system is integrated into the PGM-FI module, eliminating the need for a manual choke.
Four waterproof transistorized direct-ignition coils integrate the spark plug cap and the high-tension lead to produce a high-voltage, long-duration spark, providing maximum performance at high engine-output levels.
Iridium-tip spark plugs produce maximum spark performance and minimal carbon build-up for consistent engine operation and long spark plug life.
Powerful, compact oil-cooled alternator contributes to the engine's lightweight design.
Oil pump is driven by the alternator, further contributing to the engine's lightweight design.
Stainless steel oil cooler.
Engine cooling system allows water from the jet pump to circulate through two separate circuits to cool the engine and exhaust manifold, ensuring consistent operating temperatures for each system.
Unique three-way coolant coupler and specially designed discharge outlet reduce engine coolant flow during idling and low-speed operation to prevent over-cooling, assuring smooth operation and low emissions. A one-way valve permits simplified coolant system flushing.
Dry-sump engine incorporates an oil reservoir mounted adjacent to the cylinder bank. The tank shape and location, together with a specially designed internal multi-baffle system, optimize engine lubrication under a wide variety of marine operating conditions.
A uniquely designed crankcase breather system featuring three breather chambers prevents oil from flowing out of the engine or clogging the breather system if the hull is accidentally overturned.
Engine-cooling water circulates through the turbocharger housing to enhance compressor life.
Water-cooled cast aluminum exhaust manifold contributes to total heat management and reduces exhaust noise.
Output end is directly coupled to the jet pump drive via a rubber damper, providing shock-free, efficient power transfer while minimizing lateral crankshaft load forces.
Engine power and pump characteristics are carefully matched for maximum performance without the use of power-robbing gear-reduction systems.
Axial-flow single-stage Solas 155mm jet pump with three-blade impeller is matched to the four-stroke power characteristics. A proprietary Honda impeller design and ECU control of the turbocharger waste gate minimize pump cavitation, resulting in quiet pump operation and extended impeller life.
Pump servicing features include easy-to-disassemble pump, driveshaft, and driven coupling, and an easily accessible driveshaft bearing grease fitting.