"I went to North Coronado island today with a Search and Rescue diver. We spent 2 hours
searching the NW 55-60% of the island. It's definitely a washing machine, even in today's
modest swell, but no debris on the bottom. Depths were 40 to 60 feet. Visibility was excellent
with the exception of foam and bubbles form agitated sea-water. The diver was extremely
skilled. We saw nothing. Our experience suggests that something would have gone to the
bottom at the crash site. The mystery continues.... "

http://www.sailinganarchy.com/index_page1.php

I would think that if the boat had hit that northwest corner of the island, the keel and perhaps the engine would be somewhere in the area... So the mystery indeed continues.