Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 23Get this manual
7Turn engine over (place spark plug opening down) and pour engine oil into throat of carburetors while rotating flywheel to distribute oil throughout crankcase 8Again turn engine over and pour approximately one teaspoon of engine oil into each spark plug openingAgain rotate flywheel to distribute oil in cylinders9Remove and clean carburetors and fuel pump assembly 10Reinstall spark plugs, carburetors and fuel pump 11 .Attempt to start engi ne, using fresh fuel sourceIf engine starts, it should be run for at least one hour to eliminate any water in engine 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 engine 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 willin effectbecome too largeConsequently, the engine operates at less than its recommended RPM Due to the horsepower RPM characteristics of an enginethis will result in further loss of horsepower at the propeller with another decrease in boat speed This secondary loss, however, can be rega ined by switching to smaller pitch propeller that allows the engine to again run at recommended RPM For boaters to realize optimum engine performance under changing weather conditions, it is essential that the engine be propped to allow it to operate at or near the top end of the recommended maximum RPM range at wide-open-throttleNot only does this allow the engine to develop full power, but equally important is the fact that the engine also will be operating in an RPM range that discourages damaging detonationThis, of course, enhances overall reliability and durability of the engine