I wasn't expecting such a great response - thanks guys
I guess I ought to tie things down a bit!
VW say the max towing weight is 1500kg, but the 85% figure is 1330kg.
That's all very well, but pulling something that heavy up a slip isn't going to be easy with 2WD.
My budget is around the 8-10k mark. Therefore, I'm looking at second-hand boats.
My father-in-law is owed a big favour by a local Mercury dealer so I may be able to get an Optimax 150 at cost price or even less? (If anyone knows how much the trade price is, I'd really like to hear from them!)