Sorry to hear that!
How much cranking did you do trying to get the motor started and did you shut off the raw water intake?
Cranking excessively with the intake open can pull water into the motor without enough pressure to eject it the through the exhaust and "hydrolock" the motor. Usually it will bend a connecting rod, but I suppose it could crack a piston.
Based on your description above, I was thinking fuel quality/delivery... Certainly not a
split piston.
Hope you get it sorted out quickly.
