MMsailor,
That crack could have very well happened during transport of the engine on the motor mount. With the back end of the boat and trailer bouncing going down the road, think about it. One way to help prevent that is to take a rope, oops, line, tie it to the motor and some where tied upward to the back end of the boat to help reduce that motor from bouncing.
As for the crack, you can dremel it out just thru the gel coat only, fill with epoxy and sand smooth. If it cannot be seen, go buy a can of Krylon Fusion white paint that closely matches and spray paint but do mask off the boat so no over spray will adhere to the boat.