Weil McLain gold series one water temperature

My plumber and I am a electrician, have been throwing parts at this system without success. The boiler is in my home. Problem is boiler temperature. Will not reach even 160* the high limit which is new is set at 180* and was the first part the rep from Weil McLain said to replace. Next was the return water temp sensor. This morning we replaced the control. (1030-200). Same problem. We are at a loss. Weil McLain tech service is not very good. Any ideas? System circulators work. The burner just shuts down before reaching 180* and will not re-fire till around 120*. We also jumped out the limit that is on top of the boiler under the circulator and the results were the same.