Mercruiser 5.7 alpha 1 pees but still getting hot

by Lanny Anderson
(Clermont, Fl )

So my family and I were going to have a day out on the boat, an 88 Searay s23 open bow. Before we left home., I checked out the boat and cranked it up to make sure all was ok before I got it to the ramp and found something there.

All seemed to be good. So off we went to the lake. Put the boat in the water at the lake and the wife parked the truck and trailer., while I pulled the boat over to the slips. While sitting at the slips, I noticed the temp gauge getting higher. Pretty quick the alarm sounded and the temp gauge was pegged out.
Relaoded the boat and took it home. Hooked the hose back uo to it and just like before we left to go to the lake, it was pissing while running, just as normal...only...its still overheating.
Can anyone shead some light on this for me?