2008 Evinrude E-TEC 55MFE Technical Manual, Page 36Get this manual
INSTALLATION AND PREDELIVERY OUTBOARD INSTALLATION Transom Height Make sure the transom height matches the length of the outboard to be installed 19 to 21 in(48.3 to 53.3 cm) transom height uses 20 in(50.8 cm) shaft outboard The shaft length of the outboard being installed should come close to matching the transom height of the boatDetermine transom height by measuring from the top edge of the transom, along the centerlineUse straightedge as reference to extend the bottom of the boatPosition the straightedge along centerlineThe distance from the top edge of the straightedge to the top edge of the transom is the actual transom height1