Once upon a time, we were in Scotland and buying stuff at the local RNLI station to support the organization and they had things we wanted.
We ended up getting a tour of the "life boat" which was an amazing vessel. It has been awhile, but at cruising speed the boat was burning 100-200 GPH as I remember. They could not go far, 250 NM or so, but they could get there pretty fast. The "pilot house" was out of a space ship with the electronics, seats that keep one in place in heavy seas, along with seat belts.
I don't remember there there being much space above or below decks but they could pack in over 100 survivors if they had too. If they were around 50 survivors the boat would still self right in a capsize. There was one small, tight head, which is what you want on that vessel. The engine room was very nice, large and easy access with two big engines but there was not much space for humans.
Trying to convert that boat class to a long range cruising vessel would be huge undertaking. The power train would have to be replaced and running at under hull speed would likely not be fun with that hull design.
The vessel is an amazing piece of engineering to rescue people in horrible sea states. Not sure it would make a good cruising boat.
The night after our tour of the "lifeboat" it went out on a shout as they say. We were in Campbeltown, Scotland which is on the Mull of Kintyre with Northern Ireland just across the North Channel. Two idiots went out in a 16-20 foot, low free board power boat, to go get alcohol in Northern Ireland.
They go into trouble, surprise surprise surprise, and managed to get a call out for a rescue, which I think was done on a cell phone. They easily could have been swept out to sea on an out going tide. The two idiots were very lucky to get rescued.
Campbeltown had two very good distilleries at the time.
We saw the rescued boat the next morning, and as one of the RNLI crew whom we had met the day before said, he would have felt unsafe in the boat in the sea loch at Campbeltown. The rescued boat was really for small lakes.
The cost of the fuel used by the RNLI boat very likely exceeded the value of the rescued boat.
Later,
Dan