Sportjet 90 - Is this more than dirty carbs?

[bkhitchens]

Sportjet 90 - just replaced stator, good spark. Took it to the lake and started up just fine. I was just about ready to turn the boy loose in it and it abruptly died. It wouldn't start, although I still had spark. I was able to get it running by spraying pre-mix gasoline into the carbs and it appeared that the carbs weren't providing enough gas. I got it running again and thought it was a case of the carbs just needing to get the fogging out of them, etc. It would run okay until it was turned off and then it needed pre-mix introduced again. My daughter took it out and when she hit a wave it died. From that point on, I could get it started only with pre-mix and with the throttle advanced. It would never stay running at idle. It would never get up on plane from that point, either.

I believe that I probably blew a head gasket with all the pre-mix. I did it last year with ether.

My question is if this is just a case of diry carbs or something more? Any help would be appreciated.