For longest range, the Merlin does 110 TAS, but that is after you shut down #3 engine, it increases range by 7%, more or less. If you use 3 engines you make 120 TAS, but range is reduced. Our max fuel is around 5000 Kg to comply with MTOW, but we could carry 5300.
Payload ,with unnecessary stuff left on the ground, is enough to carry all SAR equipment, 2 pilots, winch operator + winchman, and because of PtAF regulations we still carry a doctor and a nurse for SAR! Space inside the cabin is not a problem...
You won't carry top cover from now on? We always take a C-295 or a P-3 to the longest ones, they fly ahead, identify/search the target and pass the coordinates to us. When the target is small, and the weather is bad, it makes all the difference. We've been averaging less than 30 minutes on top of the ships on the medevacs, and it's only because of this.
Also, I've had a nasty failure in the main rotor 250 miles from land, at night, and we had a P-3 on our wing on the way back, we weren't sure we'd make it, and we were 450 miles West of the other Alert Merlin in the Azores, at 500 feet with no comms, so in terms of safety, it's certainly a plus!
I remember reading somewhere a 300 miles range for the S-92, and looking at your SRR to the North/Northwest there is a lot of open sea, hence my original question.