A grid (100) is for a tunnel thruster (200). The grid (100) includes a plurality of first radially extending bars (101) arranged at angular intervals from each other, and a plurality of first connecting bars (102). Each of the first connecting bars (102) are connected between adjacent first radially extending bars (101).

A built-in propulsion system includes an engine, a diversion unit with a diversion base and an exhaust pipe, and a propulsion unit. The diversion base is connected to the engine, having a water inlet, a water outlet, a diversion channel in communication between the water inlet and the water outlet, a shaft hole above the water inlet and an exhaust chamber behind the shaft hole. The exhaust pipe is fixed on the outer periphery surface of the diversion base in communication with the exhaust chamber. The propulsion unit includes a transmission shaft inserted through the shaft hole and connected to the engine, and an impeller located in the diversion channel and connected to the transmission shaft. The exhaust pipe is used to exhaust the exhaust gas of the engine to the outside of the diversion base to avoid the interference of the exhaust gas and the water flow.

An objective of the present invention is to provide an underwater ship attachment that is used to divert air, debris, and pressure fluctuations. More specifically, the present invention discloses an anti-cavitation device (such as a diverter device) for flat-bottom boats. The air diverter has been developed to regain, enhance, and protect the operational function of propulsive and steering equipment among displacement and semi displacement hulls. As with protect items such as bottom mounted depth sounder transducers, intakes for engine or general cooling, sea chests, keel coolers, zincs, and all other underwater mounted items susceptible to air ingestion, air disturbance malfunction or debris impact.

An outboard drive assembly for a work boat is provided. In embodiments, an outboard drive assembly includes a lower outdrive assembly including: a housing extending between a first and end a second end and having a motor housed therein; a propeller mounted to the first end of the housing; first and second fins extending horizontally from opposing side portions of the motor housing; a third fin extending vertically from the housing; respective cutting blades attached to respective end portions of each of the first, second and third fins adjacent the propeller; an upper outdrive assembly including mounting brackets configure to connect the upper drive assembly to a deck of a work boat; and a drive arm assembly pivotally mounted to the lower outdrive assembly at a first end of the drive arm assembly and mounted to the upper outdrive assembly at a second end of the drive arm assembly.

Disclosed are devices, methods and/or systems for use in protecting items and/or structures that are exposed to, submerged and/or partially submerged in aquatic environments from contamination and/or fouling due to the incursion and/or colonization by specific types and/or kinds of biologic organisms and/or plants, including the protection from micro- and/or macro-fouling for extended periods of time of exposure to aquatic environments.

A propeller shield to selectively shield rotating blades of a propeller. The propeller shield may include a shield element for placement adjacent to the propeller blades. The shield element may include multiple gates configured to open in response to water flow generated by the propeller. The gates may be configured to open away from the propeller in response to a forward movement of the boat, and to close towards the propeller in response to cessation of the forward movement.

Disclosed are devices, methods and/or systems for use in protecting items and/or structures that are exposed to, submerged and/or partially submerged in aquatic environments from contamination and/or fouling due to the incursion and/or colonization by specific types and/or kinds of biologic organisms and/or plants, including the protection from micro- and/or macro-fouling for extended periods of time of exposure to aquatic environments.

A silicone bond coat composition having a viscosity of less than 1,600 centistokes is applied to substantially all external surfaces of the article and then cured. A liquid silicone elastomer outer coat composition comprising a high viscosity first liquid silicone elastomer formulation and a low viscosity second liquid silicone elastomer formulation is then applied and cured to provide a protected article having a complex shape. Optimal coatings result from a careful balancing of component viscosities. In an embodiment, the first formulation has a viscosity greater than 300,000 centistokes, and the second formulation has a viscosity less than 6,000 centistokes, and the liquid silicone elastomer outer coat composition comprises from about 60 to about 40 percent by weight of the first formulation and from about 40 to about 60 percent by weight of the second liquid silicone elastomer formulation.

A system for cutting marine grasses, weeds and other plant life to protect a propeller drive watercraft is disclosed. An adjustable, protective cutting edge to protect a propeller, drive shaft of a boat or other watercraft motor is further disclosed. A propeller protection device to mount upon a watercraft is further disclosed for optimizing the navigation of watercraft and reducing in-piloting maintenance of clearing plant matter from a propeller of a watercraft.

A boat propeller includes a gear box, an impeller, a stream-guiding ring, and a stream-shaping nozzle. The gear box has a casing and a transmission shaft partially received in the casing. The impeller has an impeller shaft and vanes. The impeller shaft has a hollow columnar outer shaft housing and a hollow columnar inner shaft housing. The inner and outer shaft housings are connected using a plurality of rib portions. The inner shaft housing is further connected to the transmission shaft of the gear box. The vanes are integrated formed on an outer peripheral surface of the outer shaft. The stream-guiding ring is assembled to the casing of the gear box to house the impeller. The stream-shaping nozzle is connected to a rear end of the stream-guiding ring for providing stream-shaping effects. Thereby, the boat propeller has its water inlet diameter maximized, which helps to improve propulsive efficiency.