No sir, it is not possible for your battery (still the 2yr old Deka 24M7?) to have 1000CCA. See East Penn's spec sheet, the 24M7 is right at the top - https://www.eastpennmanufacturing.co...Sheet-0194.pdf

Brand new, that battery had 800CCA, 1000MCA, & 130min RC.

Beg or borrow a gp31 battery with a verified 900+ CCA and see what happens. Your latest reply, IMHO, indicates classic signs of inadequate capacity, something I addressed as a concern in my 4/2/20 reply to your original post in the Mercury Motors forum.