Engineering, depending on the discipline, is on the scale of 140-200k right now, which translates to $80-$100/hr
Also don't try to force traditional business rules like 9a-5pm hours, most engineers tend to have flexible hours, be more focused on outcomes than hours.
I feel like an hour of consulting work at that rate is slightly different. I personally wouldn't expect to bill for 2000 hours of work in a single year as a contractor.
As a technical co-founder, I would expect the full 200k/yr as salary, plus equity and a cash bonus if goals are met.
Also don't try to force traditional business rules like 9a-5pm hours, most engineers tend to have flexible hours, be more focused on outcomes than hours.