The three most important factors to consider when repowering an older Grady-White with four stroke power are:
Older Grady-White boats were designed for the lighter two stroke engines available at the time. Before purchasing the heavier four stroke engines, we recommend simulating the additional weight of the four stroke engine(s), while the boat is at rest in the water, to see how the additional weight affects the waterline of the boat.
On older twin engine boats, the two stroke engines are mounted on 26" centers. This means there are 26 inches in between the midpoint of the location of where each engine is mounted on the transom. Because the engine block and cowlings of the four strokes are wider, the engines must be mounted further apart: 28 1/2" for transom mounted engines and 29" for twin engine bracketed boats. Engine centers do not apply to single engine installations.
Even with the best maintained boat, it is good practice to have a qualified marine technician administer the installation of any engine repower. Your local Grady-White dealer can also assist with engine repowering suggestions. Find your dealer here.