I assume you hooked the new starter up to the old main big wire without removing it off the old solenoid?
If so, you were trying to start through two solenoids in series(w the old one disconnected/not working).
So, to still re-use the old big starter wire on the new starter and bypass the old solenoid, just remove the big main starter wire's ring lug from the old solenoid's nearest to transom stud(as view in your pic here) and move it to the closest stud(as view in your pic here)placing it with and over the top of the existing batt. wire I've indicated in the call out note on your pic below.
When moved/done, both main big red wires(as seen here in the first pic) then will be bolted on this same stud together. They can live happily ever after bolted together there on that ole stud of you like and your trim/tilt solenoids, etc. will still continue to have their batt. feeds as well.
