Bombers like the B-17 and B-24 were regularly used at maritime scout planes looking for Japanese ships, as their long range made them suitable for the task along with the PBY.
ack-ack
Or just go with the PB4Y-2 Privateer, 6 turrets with 12x .50 cals over all, bombload something like 12,000lbs
It was a maritime patrol bomber used in late ww2, not sure how many squadrons were in use, but it sounds like a hell of a better option then the PBY.
I do know a few hundred will built overall (not sure war-wise) and it flew up to 275mph+.
The only kicker was, it did not have turbosuperchargers, so I don't think the plane flew well above 15k.