2006 5.7 ETX-CAT thermostat bolt removal

Been a long time since I've been on here. 2 moves, a baby... Life.

I was out two weeks ago and watch temp rise and ecm took throttle back to idle to cool. Ok no prob 8mph back to dock.

Plan to check impeller and change thermostat.

How do you get good access to the two larger bolta on the thermostat? After being torqued and painted mine are super tight and can watch the 9/16 wrench flex and skip off bolt. Tried with two sockets both seem to want to slip off and worried about stripping the head. Engine cover prevents me from getting full perpendicular on the bolts.

Small bolt loosened no problem. Can get better angle on starboard bolt, butport bolt is being a PITA.

Any tips on what ppl have used to remove? Craftsman sockets and Kobalt wrenches keep wanting to slip off.

Did u remove engine cover (top plate)?