I am currently running a 90 Mariner 2 stroke, the Searider we took round Britain had a 90 Merc 4 stroke. The later obviously was much more fuel-efficient. Due to wait and constant pounding a transom bracket is a good idea, you will need to get it sized and made yourself but a dam good idea, The Humber Assault on RB4 needed one as the transom started to go but it's still a great rig in my opinion. 4 Stroke's are more expensive, if you are buying 2nd hand you will probably end up with 2 stroke, (depending on how much you spend)!.
I paid £5200 for mine, 11-year-old boat, 5-year-old engine, have since replaced the trailer and added fancy electric bit's. Where the F**K are we box and VHF. The trailer has been the best bit of kit I have bought, decent slip I can launch and Retrieve on my own without any hassle.
As for speed on my own on the flat I can push 38knots with the wind behind me!
Good cruising speed about 22-24 in moderate conditions, and can still do 16 -18's in the fairly ruff (thatís with some fairly determined helming)!
I will look to replace my tubes this or next year and re do the A frame. and seating arrangements.
So depending on your budget and level of bashing you want to give the thing will depend on hoe much you continue to spend once you have had made your initial purchase!