Mercury Mariner Outboards 2.2 / 2.5 / 3.0 Service Shop Manual, Page 15Get this manual
IMPORTANT: When storing outboard for the winter, be sure that all water drain holes in gear housing are open and free so that all water will drain outTrapped water may freeze and expand, thus cracking gear housing andor water pump housingCheck and refill gear housing with Quicksilver Gear Lube before storage to protect against possible water leakage into gear housingInspect gaskets under lubricant vent and fill plugs, replacing any damaged gaskets, before reinstalling plugs Summer conditions of high temperature, low barometric pressure and high humidity all combine to reduce the engine powerThis, in turn, is reflected in decreased boat speeds as much as or miles-per-hour in some cases(Refer to chart Nothing will regain this speed for the boater, but the coming of cool, dry weatherIn pointing out the practical consequences of weather effects, an engine running on hot, humid summer day may counter loss of as much as 14 of the horsepower it would produce on dry, brisk spring or fall dayThe horsepower, that any internal combustion engine produces, depends upon the density of the air that it consumes and, in turn, this density is dependent upon the temperature of the air, its barometric pressure and water vapor (or humidity) contentAccompanying this weather-inspired loss of power is second but more subtle lossAt rigging time in early spring, the outboard was equipped with propeller that allowed the engine to turn within its recommended RPM range at full throttleWith the coming of the summer weather and the consequent drop in available horsepower, this propeller will, in effect, become too largeConsequently, the engine operates at less than its recommended RPM Due to the horsepowerRPM characteristics of an engine, this will result in further loss of horsepower at the propeller with another decrease in boat speedThis secondary loss, however, can be regained by switching to smaller pitch propeller that allows the engine to again run at recommended RPMRefer to "Propeller Selection ," following