Does anyone have the cutout dimension for an old Hynautic BH Series helm pump?

I need to make new mounting plate and am 1000 miles from the boat and
installation sheet.

The dimension I need is the diameter of the pump cutout which is between 3.25
and 3.75 inches. I need to get it exact as the clearance for the mounting
screws is less that 0.25" outside the mounting plate.

Ironically, all of the old pump dimensions are on the Seastarsteering.com web
site except this one which leads to a dead link.

TIA for any help.