Thanks for all the replies - yes I am new to the rib world - I am switching from a Sealine S34 to a rib as we are not overnighting much on the boat anymore like we used to do and fuel cost/ maintenance / mooring do no longer have good justification. We have also visited lots of places in the south coast so the idea of a rib is that in the longer term being able to trailer it and explore more places.
However, for the first season, we will still keep the rib in the Solent.
Having said that, last weekend I used my dinghy with a 5hp outboard near hythe and it was good enough! so 100hp is surely good!!!