Well, I'll take a WAG (wild ass guess)....HOT water probably indicates that the water has passed through the engine so I'd guess there is a leak in the water exhaust side of the system perhaps?
I myself have a 2017 Spark 2 that I dropped in the water on Friday night, ( I completely replaced the hull this winter on that ski after a mishap last season), my son rode it Friday evening no issues, started, ran fine.....all fixed I thought. After being in the water an hour or so, my wife makes the comment, "it looks like its sitting LOW in the water on the rear end". Looked OK to me. Woke up Saturday morning and the ski was squating in the water up to the rear deck....Uh oh! Pulled the ski out, did not start it or open the drain valve since I was hoping to see where the water might be dripping out of the ski....sure enough, the ski was dripping for an hour but I can't really pinpoint the leak source.....I'll have to take the top and rear decks off and put some water in there to try to isolate the leak point....I tried to make sure I gobbered up all the hull penetrations with lots of sealant as I re-assembled the ski...but I obviously missed something somewhere.....SIGH!!!!! but she runs !!!!!