A marine propulsion unit is described. The marine propulsion unit allows for shallow, obstructed, or otherwise impeded operation of a vessel through a novel marine propulsion transfer unit that is, or can be, mechanically coupled to an outboard motor or other similar marine motor. A mount for raising and lowering the marine propulsion unit in a generally vertical direction allows for adjustment of operating depth of the marine propulsion unit to accommodate a wide range of operating conditions from shallow and obstructed water to traditional deep water operation.

A marine propulsion unit is described. The marine propulsion unit allows for shallow, obstructed, or otherwise impeded operation of a vessel through a novel marine propulsion transfer unit that is, or can be, mechanically coupled to an outboard motor or other similar marine motor. A mount for raising and lowering the marine propulsion unit in a generally vertical direction allows for adjustment of operating depth of the marine propulsion unit to accommodate a wide range of operating conditions from shallow and obstructed water to traditional deep water operation.

In an embodiment, a helm device comprises a steering shaft extending in a first direction, a housing, a tilt base, a pair of tilt mechanisms which supports the housing to make the housing rotatable with respect to the tilt base about a tilt axis, and a lock mechanism which fixes an angle of the steering shaft. Each of the pair of tilt mechanisms comprises a shaft member projecting from a side portion of the housing, a bracket provided on the tilt base and comprising a hole portion into which the shaft member is inserted rotatably, and a bushing disposed between the shaft member and the hole portion.

In an embodiment, a helm device comprises a steering shaft extending in a first direction, a housing, a tilt base, a pair of tilt mechanisms which supports the housing to make the housing rotatable with respect to the tilt base about a tilt axis, and a lock mechanism which fixes an angle of the steering shaft. Each of the pair of tilt mechanisms comprises a shaft member projecting from a side portion of the housing, a bracket provided on the tilt base and comprising a hole portion into which the shaft member is inserted rotatably, and a bushing disposed between the shaft member and the hole portion.

A method of controlling tilt-trim position of a trimmable device on a marine vessel includes receiving an engine speed, a vessel speed, a vessel pitch, and/or a vessel acceleration. A trim rate is then determined based on the engine speed, the vessel speed, the vessel pitch, and/or the vessel acceleration. The trim rate specifies a rate of rotation of the trimmable device about a horizontal axis, and the trim rate is determined such that the rate of rotation is minimized at high vessel speeds and high engine speeds and the rate of rotation is maximized at low vessel speeds and low engine speeds. A variable speed trim actuator is then controlled to rotate the trimmable device based on the trim rate so as to adjust a trim position of the trimmable device.

A method of controlling tilt-trim position of a trimmable device on a marine vessel includes receiving an engine speed, a vessel speed, a vessel pitch, and/or a vessel acceleration. A trim rate is then determined based on the engine speed, the vessel speed, the vessel pitch, and/or the vessel acceleration. The trim rate specifies a rate of rotation of the trimmable device about a horizontal axis, and the trim rate is determined such that the rate of rotation is minimized at high vessel speeds and high engine speeds and the rate of rotation is maximized at low vessel speeds and low engine speeds. A variable speed trim actuator is then controlled to rotate the trimmable device based on the trim rate so as to adjust a trim position of the trimmable device.

A hull mounted, steerable marine drive system having trim actuation is both steerable through 360 degrees and is trimmable. The marine drive system includes a watertight enclosure assembly for sealing the hull, which is adapted for keeping much of the marine drive system from being exposed to water. The enclosure includes a gasket flange plate, a retention plate and a folded gasket. The gasket flange plate closely follows the contour of the hull and enhances the hydrodynamic and wake performance of the present marine drive system. Further, marine drive system includes a forward-neutral-reverse (FNR) transmission assembly, a drive unit assembly having a trimmable upper unit and a steerable lower unit, a steering actuator assembly, a trim actuator assembly, and, preferably, trim foils for providing enhanced negative and positive trim and for providing enhanced positive and negative lift.

A hull mounted, steerable marine drive system having trim actuation is both steerable through 360 degrees and is trimmable. The marine drive system includes a watertight enclosure assembly for sealing the hull, which is adapted for keeping much of the marine drive system from being exposed to water. The enclosure includes a gasket flange plate, a retention plate and a folded gasket. The gasket flange plate closely follows the contour of the hull and enhances the hydrodynamic and wake performance of the present marine drive system. Further, marine drive system includes a forward-neutral-reverse (FNR) transmission assembly, a drive unit assembly having a trimmable upper unit and a steerable lower unit, a steering actuator assembly, a trim actuator assembly, and, preferably, trim foils for providing enhanced negative and positive trim and for providing enhanced positive and negative lift.

A method of automatically controlling trim position of a marine drive with a control system on a marine vessel includes receiving a user-selected command associated with wake surfing and then controlling a trim actuator to automatically position the marine drive in a tucked position, tucked position is between a vertical trim position and a minimum running trim position. Once a vessel condition of the marine vessel reaches a first threshold vessel condition the trim actuator is controlled to trim up the marine drive to a predetermined target trim position to generate wave behind the marine vessel. The first threshold vessel condition is at least one of a threshold vessel speed, a threshold engine speed, a threshold engine load, and a threshold vessel pitch.

A method of automatically controlling trim position of a marine drive with a control system on a marine vessel includes receiving a user-selected command associated with wake surfing and then controlling a trim actuator to automatically position the marine drive in a tucked position, tucked position is between a vertical trim position and a minimum running trim position. Once a vessel condition of the marine vessel reaches a first threshold vessel condition the trim actuator is controlled to trim up the marine drive to a predetermined target trim position to generate wave behind the marine vessel. The first threshold vessel condition is at least one of a threshold vessel speed, a threshold engine speed, a threshold engine load, and a threshold vessel pitch.