I've got a Zodiac 2.85m solid floor with a Mercury 6hp 4 stroke and it planes easily with 2 of us on board, achieving 14.5mph on the GPS. That's with me sat on the tube at the rear and my wife on the seat at the front. I've not tried it with just one person on board but I imagine it would be a bit faster.
The boat has a V-floor similar to the air deck version, but has a solid wood floor over the top. The engine weighs 26kg and is easy to carry/fit on the boat.
Mercury do a 4, 5 and 6hp version of this engine and they all look identical, except that the 5 and 6 hp have an external fuel tank. I think Mariner and Tohatsu do pretty much the same engine with their name on it. I'm not sure how the 4 and 5 hp versions would perform regarding planing/boat speed though.
Motor Boat Monthly did a test of small (2.6m and 2.7m) SIBs recently and there was quite a difference in performance between boats, using the same engine (a 5hp). All would plane with one person and a 5hp, but most struggled with 2 persons. They also tested the boats with a 2.5hp and none would really get on the plane with one person, except a Sunsport which managed 10mph.