Not much activity on this forum this year.
Did you ever solve this problem?
My skis are older than yours, but in general....
Leaks are either bad coolling hoses or connections, bad driveshaft bearing seals or mount, or bad thru-hull fittings or cables (trim / reverse cables). You already ruled out drain plug or hull damage, and you don't even want to think about a cracked block.
If its leaking that bad, just stand in shallow water and look inside. Or haul it out on the trailer with water inside (careful... too much water can overload the trailer design) and look to see where it drains OUT.