new engine issues - cranking but not turning over

We launched our boat today and it started right away but stalled out after 15-20 seconds - after that it would crank fine but would not turn over. Fortunately there is a dock right near the ramp and we got the boat tied up. We tried to start the engine several more times, then it started to rain. We were about to go back home, but I decided to try one last time and the engine turned right over. We ran it for several minutes in neutral at 2000 RPM and higher with no problem at all.

Unfortunately a thunderstorm was coming in so we had to head home and leave the boat at the dock. As soon as it cleared up we went back to the boat but it would not turn over. After 10 attempts or so it turned over once, but stalled out after a few seconds. Afterwards it would not turn over again.

It is a brand new engine and the fuel pump is brand new as well. Any ideas? Of course it is a holiday weekend and we won't be able to get in touch with the dealer until Tuesday. Any suggestions or thoughts that might get us up and running for Sunday and Monday are much appreciated! Thanks.