Dont listen to Stormin, you have not proved the thermost is bad and alt
Hvac is Not the place.
"The Wall" is.
But here is an idea. Is the boiler running constantly, what temp is the
aqua stat at, what is the temp and water height, " altitude " on the
gauge, Is the recirculator pump running. Did you bleed the radiators of
air, are they hot to the top. Answer these first.
But honestly you need a tech for a system review-clean-setup-homeowner
lesson. And for your education so you Know whats what. Ignorance can
ruin a boiler in many ways.