Pics of the gasket and the head and block.
What were the bolts tuorqed to?
The bolts holding the exhaust chest on are 1/4-20 and might be tricky to remove.
You'll need to take it off and see if the gasket's gone bad.
Is the snout still on the lower unit?
I heard one time a guy lost his and it caused the motor to suck up some water.
Backfiring?
Something to try: Silicone (lots)on the old gasket, torque to 20#
Do a compression test.
Go for a ride and see if it happens again.
