MARINE-TEX! Tape off an area 1/4" larger than the footprint of the shaft log. Then thru bolt the log with the sealer in place, clean up. Fuel, oil, water and VIBRATION will not affect it's sealing powers! Silicone will melt away in fuel, oil, gear oil, Jack Daniels. I thru bolt and Marine-tex, NEVER any leaks!
Where do I get this it sound bullet proof?