1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 366Get this manual
Installing Outboard Motor on Transom Determining Recommended Outboard Mounting Height
aThis solid line is recommended to determine the outboard mounting height dimensionUse transom mounting bolt holes that will position outboard nearest to the recommended heightAfter engine break-in (if necessary), raise or lower outboard one position at time to attain best performanceSee "Important" immediately followingIMPORTANT: Increasing the height of outboard generally will provide the following: 1) Less steering torque, 2) more top speed, 3) greater boat stability, but, 4) will cause more prop "break loose" which may be particularly noticeable when planing off or with loadThese broken lines represent the extremes of known successful outboard mounting height dimensionsThis line may be preferred to determine outboard mounting height dimension, if maximum speed is the only objectiveThis line may be preferred to determine outboard mounting height dimension for dual outboard installationOutboard mounting height (height of outboard transom bracket from bottom of boat transom)For heights over 22 in(560mm), propeller, that is specifically designed for surfacing operation, such as the "Chopper" series, usually is preferred