Tim, we bought a prop wrench from Steel Developments which has the benefit of floating so if you ever need to change the prop at sea, at least you won't be bu**ered if you drop it in the water! According to their website, you need a 15/16" or 24mm one. http://www.steeldevelopments.com/Acc...for_boats.html
We also bought a 'prop change kit' from them which contains spare thrust washer, split pin, castellated nut.
BTW, your local Mariner dealer will probably stock all this and may well be cheaper!
Dave Crawford Marine (Lymington) & Lee Fairweather (Fareham) usually have these on their shelves.