I have been troubleshooting my own vapor lock issue and saw this thread here: http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/vapor-lock-coil-issue-462782.html. Mine is on a carbuerated 4.3 merc though. Can a fuel cooler be installed on my engine do you know? I have the same problem as you BIGALF, starts fine the first start of the day, but after running a while and stopping, it cranks and cranks. Yesterday I had to take the flame arrestor off and open the butterfly to get it going.