Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 325Get this manual
Installing the Outboard Determining Recommended Outboard Mounting Height
Boat instability can occur at high speeds by installing engine at the wrong transom heightContact the boat manufacturer for their recommendations for specific engine installation
Outboard Mounting Height (See NOTE Below)
24 in(609mm)
21 in(533mm)
20io(508mm)
19 in(482mm)