Abstract: An exhaust system for marine propulsion units passes engine exhaust gas out through lateral holes in the lower unit casing at the level of the propeller shaft that communicate between an exhaust passage in the propeller-shaft-support unit and the ambient water. This venting mechanism discharges gas at the level of the propeller hub when the vessel is moving slowly. The vented gas enables the engine to rapidly increase its RPM s without excessive engine loading. This allows for increased acceleration and less engine damage. The system may include venting gas though the hub and out the aft end of the propeller. The system may be used with outboard engines, inboard/outdrives, and full inboards. When used with full inboards, a valve mechanism may enable diversion of an adjustable fraction of the exhaust gas through the transom. A drain hole may also be provided to drain water from the gas passage when the lower unit is out of the water.

Abstract: A novel bottom configuration for a V-type planing hull which consists of a V-shaped section which extends from the bow to a shoulder located aft of amidships, and a section aft of the shoulder consisting of a partial continuation of the V-sidewalls, joined by a generally horizontal bottom wall which extends to the transom.