Mercury Mariner 4, 5 102CC Sail 1990 Outboard Service Shop Manual, Page 11Get this manual
IMPORT ANT: When storing outboard tor the winter, be sure that all waler drain holes in gear housing are open and tree so that all water will drain outTrapped water may freeze and expand, thus cracking gear housing and or water pump housingCheck and refill gear housing with Quicksilver Gear Lube before storage to protect against possible water leakage into gear housinglnspect 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 turnis reflected in decreased boat speeds as much as or miles-perhour in some cases(Refer to chart Nothing wi ll regai th is speed for the boater, but the com ing of cool, ry weatherIn pointing out the practical consequences of weather effects, an engine running on hot, hum id summer day may co unter loss of as much as 14 of the orsepower it would roduce on drybrisk sp ri ng or fall dayThe horsepower, that any internal combustion engine produces, depends upon the density of the air that it consumes and, in tu rnthis density is dependent upon the temperature the air, its barometric pressu re and water vapor (or humid ity) contentAccompanying this weather-inspired loss of power is second but more subt le loss At rigging time in ea rly springthe outboa rd was equipped willIpropeller that allowed the engine to turn with in its recommend ed RPM range at ull throttleWith the coming the um mer weather and the consequent drop in avail able horsepower, th is propeller will, in efiect, become too largeConsequently, the engi ne operates at less than it recommended RPM Due to he horsepowerRPM haracteristics of an engine, this wi ll result in further loss of horsepower at the propeller with another dec rease in boat speedThi seconda ry loss, owever, can be regained by swi tc ing to maller pitch propeller that allows the engine to again run at recommend ed RPM Refer toPrope ller Selection ," foll owing