A shrouded outdrive propels a high-speed boat having a
hull for high-speed passage through water. The
hull has at least one bow at the forward end and at least one transom at the
stern. A tubular shaft extends at a small angle (6° to 12°) from the boat transom into the water, and a
drive shaft is arranged within the tubular shaft. A
propeller is mounted to the
drive shaft for partial immersion in the water so that a lower portion of the
propeller extends into the water during high-speed floating passage of the boat and a upper portion of the
propeller is above the water during high-speed floating passage of the boat. A shroud is arranged about the propeller and is disposed below the water and adjacent the propeller. A
mount holds the shroud to form a shroud-enclosed channel during high-speed passage of the boat through the water in which the propeller rotates. A plate horizontal to the undisturbed passing water surface overlies the departure side of the propeller at a radial distance of about two thirds (⅔) of the
radius of the propeller. This plate immediately abuts the departure blading of the propeller in the direction of boat movement through the water and assures immersion of the lower
pitch departure side of the partially immersed propeller in water for more efficient propulsion. Embodiments are disclosed where the plate is utilized as the necessary support for the shroud. Additionally, both the shroud and the plate can have small angular variations with respect to the surface of the undisturbed surface through which the high-speed
hull passes.