Welcome to the starange world of RIBs. I know nothing about the Flatcraft series of boats. The mercury engine should serve you very well. In general they are well out together and are basically from the same stable as Yamaha.Mariner.
As to what to look out for with the boat/engine it's hard to know where to start.
I highly reccommend that you get some RYA training (if not already done). I also suggest that you purchase a copy of a book called Powerboating by Peter White, this is being updated at present, it could even be finished.
BOAT: Keep the boat washed down and covered when not in use.
1.Make sure that grit/stones and the like do not get in between the deck and sponsons, they can cause chaffing and then a leak, once in a while let the sponsons down and give the crevice a good clean out with a soft brush/hoover.
2.Make sure that any minor repairs are carried out as soon as possible.
Make sure that all lines/warps are free from tangle and ready for use.
3.Make sure the deck is clean and not slippery. Do NOT clean sponsons with any silicone based "gosh my boat is shiney" products, you passengers will not be passengers for long!
4. Keep the sponsons at the right inflation when using and dont forget that when(IF EVER) it gets hot, they will expand, so if they have been pumped up hard, they may over inflate.
5. Keep a photograph of the boat, together with serial number and details of CE Plate.
6.Keep the trailer locked when ashore, a wheel lock or clamp such as the SAS clamp is good, and you could also consider something like a Bulldog hitch lock
That's a start and I am sure that some of the other wise heads on this forum can add too it...perhaps not a bad idea to get a list together amonhst us all for newcomers...
1. Flush after use
2. Keep oil etc topped to right level
3. Keep prop in good order, a damaged prop can damage the gear box.
4. Make sure the right prop is fitted, search this forum for previos repiles to this subject.
5. Fit an engine locking device.
6. Keep it serviced.
7. When its not going to be in use for sometime, take the fule line off and run the engine dry, this will stop gunk building up in the engine.
HOPE ALL THIS HELPS..............COME ON FORUM..LETS HELP GET THISLIST RUNNING