My 60 efi will start the first time, everytime. However, after a run of 15 minutes and a shutoff, it will start but quit after a few seconds and will have to sit for 30 minutes before it will start and run. Without the cowl and cooled off, it will start and run and stop and start again all day. A hot voltage regulator maybe?

I would be more inclined to think vapor lock.
Put a piece of clear hose (temporarily) in before the motor and run it, there should be nothing but fuel in the hose, if there is air you have a leak somewhere.