Diagnostic HELP: Engine lost power, a restart fixed it??

[CobaltMinerAtl]

Diagnostic HELP: 2005 Cobalt 282, Merc 8.1, lake water boat, 3 batteries. Was out today no issues riding around. Anchored in a cove and sat for 3-4 hours. Was leaving, engine started fine, was in gear leaving the cove at idle speed. Once I started to transition to full load the engine would not increase in power, it revved up but no power, it almost stalled out. So i decided to turn the engine off and restarted it, once restarted the boat was back to normal, I was able to leave and travel back to the dock no issues. Any thoughts? See less

[kas232ca]

Maybe a spun prop?