Find a vertical centerline on the transom. Measure out each side for the new motor centerlines. Standard was 26" centers so you would go out 13" from the centerline each side. The new 4 strokes want at least a 28" engine center line so you may want to setup the holes for 4 strokes in case you repower in the future. Measure 25" up from the engine centerlines for 25" shaft length motors and this will be your final transom heighth. Make a horizontal line at this heighth and cut your transom. Be sure you have allowed enough width for steering cyllinders and cowling clearance to the outsides.
