A dual drive hybrid electric power plant to power an aircraft comprises a propulsion assembly, an internal combustion engine having an output shaft configured to drive the propulsion assembly, and an electric motor configured to drive the propulsion assembly and to be selectively coupled to the output shaft. The power plant may be configured such that the electric motor alone drives the propulsion assembly, or such that the internal combustion engine and the electric motor drive the propulsion assembly.

A dual drive hybrid electric power plant to power an aircraft comprises a propulsion assembly, an internal combustion engine having an output shaft configured to drive the propulsion assembly, and an electric motor configured to drive the propulsion assembly and to be selectively coupled to the output shaft. The power plant may be configured such that the electric motor alone drives the propulsion assembly, or such that the internal combustion engine and the electric motor drive the propulsion assembly.

A personal watercraft includes: a watercraft body including a hull and a deck covering an upper portion of the hull; a light emitter supported by the watercraft body; and a protection cover covering the light emitter and permeable to light emitted by the light emitter, wherein the watercraft body includes a flow-regulating structure, and the flow-regulating structure includes: a fluid inlet through which an external fluid enters the watercraft body; and an upper flow-regulating wall and a lower flow-regulating wall that are opposed to each other in an up-down direction, the upper and lower flow-regulating walls being located between the fluid inlet and the protection cover to regulate flow of the fluid entering the watercraft body through the fluid inlet and moving toward the protection cover.

An aircraft propulsion system comprises an engine, a propeller drive shaft drivingly engaged with the engine, a propeller for propelling an aircraft and a fan driving cooling air along a flow path in thermal communication with the engine. The engine may be an internal combustion engine or other engine type having heat rejection requirements and the fan may facilitate cooling of the engine. The propulsion system may have a pusher configuration.

An ignition timing controller includes a storage and a processor configured or programmed to function as an ignition timing control section and a knocking determining section. The storage stores at least one of a first ignition timing map associated with a first fuel or a second ignition timing map associated with a second fuel more likely to cause knocking of an internal combustion engine than the first fuel. The ignition timing control section controls the ignition timing based on the first ignition timing map by executing a timing retardation based on the first ignition timing map when it is determined that knocking of the internal combustion engine has occurred. The ignition timing control section controls the ignition timing of the internal combustion engine based on the second ignition timing map by executing a timing advancement correction based on the second ignition timing map when it is determined that the knocking of the internal combustion engine has not occurred.

An outboard motor includes an engine to rotate a propeller and an engine cover that houses the engine. The engine cover includes two divided covers disposed above the engine and that directly face the engine. The two divided covers include two connections that are connected together and that overlap the engine in a plan view.

A method of operating an engine assembly receiving fuel, including admitting atmospheric air at a temperature T.sub.1 through an inlet of a compressor having a pressure ratio of PR.sub.GT, compressing the air in the compressor, cooling the compressed air from the compressor through an intercooler to cool the air from a temperature T.sub.BIC to a temperature T.sub.AIC, delivering the cooled compressed air from the intercooler to an inlet of an intermittent internal combustion engine having an effective volumetric compression ratio r.sub.VC, and further compressing the air in the intermittent internal combustion engine before igniting the fuel, where ${\left({\mathrm{PR}}_{\mathrm{GT}}\right)}^a{\left(r_{\mathrm{VC}}\right)}^b\left(\frac{T_{\mathrm{AIC}}}{T_{\mathrm{BIC}}}\right)\left(\frac{T_1}{T_A}\right)<1.$
An engine assembly is also discussed.

A method of operating an engine assembly receiving fuel, including admitting atmospheric air at a temperature T.sub.1 through an inlet of a compressor having a pressure ratio of PR.sub.GT, compressing the air in the compressor, cooling the compressed air from the compressor through an intercooler to cool the air from a temperature T.sub.BIC to a temperature T.sub.AIC, delivering the cooled compressed air from the intercooler to an inlet of an intermittent internal combustion engine having an effective volumetric compression ratio r.sub.VC, and further compressing the air in the intermittent internal combustion engine before igniting the fuel, where ${\left({\mathrm{PR}}_{\mathrm{GT}}\right)}^a{\left(r_{\mathrm{VC}}\right)}^b\left(\frac{T_{\mathrm{AIC}}}{T_{\mathrm{BIC}}}\right)\left(\frac{T_1}{T_A}\right)<1.$
An engine assembly is also discussed.

This oil case of an outboard motor is provided below an engine and stores lubricating oil of the engine. In this method for manufacturing the oil case, the oil case is manufactured so as to comprise: an oil chamber; an introduction path that guides upward cooling supply water drawn in from outside the outboard motor; a delivery path that guides downward cooling discharge water that has cooled the engine; a main exhaust path that guides exhaust gas of the engine downward; and a sub exhaust path that guides exhaust gas during low-speed rotation of the engine. The oil chamber, the introduction path, the delivery path, the main exhaust path and the sub exhaust path form an integral structure.

An outboard motor is provided with: an engine cover in which a first outside air inlet port, an exhaust port, and second outside air inlet ports are formed; and a lower housing that is disposed below the engine cover. The engine cover is provided with a front guide and a rear guide that guide outside air, introduced respectively from the first outside air inlet port and the second outside air inlet ports into the engine cover, downward in the gravity direction.