For a 3/4 hole I use a hole saw and tape off the gel. First, after you layout the point you want it drill a very small pilot hole and check for clearance on the under side of the deck before you make your large hole. By using a small pilot hole it gives you the chance to move the location around a bit. So long as the pilot hole is within the size of the hole saw.
Gone, out doing soft recreational past time with overpowered boat!