GT40 with recurring stalling problem

Hope someone can help with this. I have a 99 Air Nautique with GT40 EFI and apprx 350 hours. The last 5 times out the boat started fine and ran perfect. Then after stopping for around 30 minutes or longer, it restarted and ran fine for 100-200 yards at which time it seemed to lose fuel and stopped. After sitting 10-20 minutes, it would restart and be OK. I have replaced fuel filter, fuel pump relay and cleaned the anti siphon valve. The fuel pumps do come on when the problems arise but the motor will not start. Took it to local marina who said they could find nothing wrong and billed me $400! Someone please help! (by the way, I am not very mechanically inclined)

Any idea what the marina did for $400???

The ignition systems on those engines have been known to be somewhat fragile...part are hard to find on top of that...

You need to figure out definitely whether the no start is ignition or fuel related as step one, IMO...

Thanks for the reply. The marina did nothing. They said that they could not recreate the problem. The boat is in great condition. I feel sure that they did not put it under the conditions that I described to them.

I'd suggest getting a timing light and a fuel pressure gauge, or buying a case of beer preferred by your bud that does.

Keep both hooked up next time you go out and use them when the issue appears to see if it is fuel or spark driven.