It does sound related, but I really don't think it is...I've been a gear head and Chevy 350 guy for a long time and it just doesn't seem like its overheating, maybe I'm wrong though

The only other difference between the land and water runs were the land run was idling for 30 minutes, the water run it was at 4k for ten minutes

I'll do the ignition stuff this weekend, if it doesn't work I'll look into valve stuff and overheating stuff