Ed I usually use 5200 for the sealant around the motor mounting holes though it is a real pain to remove sometimes and it will take paint off along with it when time to remove it. 4200 is a lot more forgiving when it's time to remove. Make sure you coat the inside of the holes with a "penetrating" epoxy prior to using sealant around the holes. Not sure if it's the proper way
Check out 3M's site they have some good info on their adhesives/sealants. They have a new one out called 4000 which is UV stable for use above deck.
http://www.shop3m.com/marine-adhesiv...fasteners.html
strick