First startup experience.

I had a strong desire to prove myself and therefore started out working 50-60+ hours off the gate. I am now working near 70/wk regularly, several months into this role.

Each week I am delegated new responsibilities I am told I will regularly own by my boss, many of which are not difficult but take more time to do and are manual, further exacerbating my workload. These tasks are things my manager used to do but “feels they now make more sense to belong to me”.

I do not have equity in this company. While I would like to do a good job, I do not want the expectation to be for me to work greater than 50 hours a week.

What is the best way to professional handle a large workload like this/ how do I respond to my boss’s requests I “start doing this one other task now”