169 isnít hot I donít think.
Your saying itís alarming at 169?
If not, how hot is it when it alarms? Iíd try a thermostat, easy and cheap. I really donít think that is it, but easy and cheap to eliminate and you may get lucky.
The air bubble thing can be tricky, it moves around and causes trouble, I assume it could move into the water pump
and make it stop pumping water.
Again, see if it has a bleeder screw and if it does open the screw and with fresh water cooling system full it should flow out coolant
, but it has to be completely full as the bleeder screw ought to be real close to the top of the system.
Iím sure googling how to bleed a Chevy cooling system will show you how, assuming the Marine
engine is reverse flow, and has bleeder screws.
My old 454ís didnít, but likely they were too old.