I just don’t know about the switch from the P-3 to the P-7 (737). Two engines versus four, less endurance, no great increase in relevant performance.
A further updated P-3 with the latest avionics would seem to me to have been the better choice. I think politics played a role.
I stand corrected. The aircraft that beat out the Orion was the P-8, a maritime patrol version of the 737.
That will come as a surprise to P-8 crews while they refuel in flight, something they couldn't do in a P-3.
The problem is P-3 airframes. They’ve had it. Designed, I believe, for 20,000 hours. Some have exceeded 60,000 and they are just worn out. The P-8 is a 737-800EX variant and no, it is not a good replacement for ASW work. It wull fly at 20,000 feet and do high altitude ASW. The problem is that high altitude ASW doesn’t work after the detection phase. The Navy wanted 156 P-8s. That is down to 107 officially. Won’t happen. Will end-up with one operational squadron on each coast plus some in HI — which will then be moved to Guam. Since 1991 we have basically abandoned ASW and AMW.