470 overheats again

[surchin]

Well I'm really bummed, so I ran her for first time after repairs. Started great sounded great ran out and around fir about 30 min at 3/4 speed turned it off floated hung out for a bit. Pulled eng cover everything looked felt good. Started her up cruised back to dock hung out a bit started it again while idling at dock suddenly just quit. No cough no chug just stopped while idling at dock. Pulled eng cover and motor was too hot to touch coolant was good no steam or leaks from anywhere.

I really thought all repairs were done well. Had it done a a shop to get it done right and couldn't do it myself anyway.
New gasket for raw water pump and new oil seals. Newused ex manifold, new used 4" heat exchanger . Risers cleaned and painted. Thermo replaced. What else is there to do to prevent overheating.? Temp gauges not working so I don't know if it all of sudden got hot or what

Where next to look for cooling problem?
Thanks
Scott