Originally Posted by Willwors
small RIB or inflatable, mainly to use as a tender... also for a bit of fun as well. Would like something quick... about 15hp and around the 3.5 metre mark
This is quite a common question, so have a search (it'll keep you busy!
) but here goes anyway...
You need to decide if you want a solid hull or a fully inflatable. Solid hulls start at about the 3.5m mark, if I remember correctly, but they aren't very deep V. This means that they will have limited sea-keeping ability (ie they will slam into waves). Fully inflatable boats (we commonly refer to them as SIBs) have an even flatter profile, and even with an inflatable keel they don't go into waves particularly well. However, they are still much better than the type with slatted wooden floors, which have a completely flat hull.
The biggest difference between solid hulls and fully inflatables is storage. If you need to store in a car boot, or in limited space on board (or back at home) then a fully inflatable boat is the one to go for.
I reckon that the best compromise at this size is a fully inflatable, with inflatable keel and floor. Zodiac make a good boat, they are the standard by which others are judged. Quicksilver make a good boat too. My personal favorite, after looking at many different brands is Lodestar http://www.lodestardirect.co.uk
As far as engines are concerned 15hp will make a 3.5m inflatable go like stink. 4-stroke if you only ever use it as a tender, 2-stroke if you intend to transport it in a car boot, and a two-stroke will be faster too - in fact it will probably scare you!
Look carefully at weights - the best package is the lightest.