Ritchie,
I wouldnt really tow above 500kgs. 700kgs would be the max but youll have clutch(m/t) or band(a/t) problems quicker than you expect. Worst come to worst being a front wheel drive, normally the diff breaks down into pieces and thats when the big money comes in.
Get a tinny. Way lighter, cheaper in petrol, you wont worry about rot, low maintainance. If it gets to choppy anyway, you wouldnt want to be out there as it wont be to comfortable.
Ive got a 17ft halfcabin glass boat (still on the side of my house) took it out 3 times in 4 yrs. Got a 4.3 tinny last year. Took it out every three weeks since September. The more the boat is cheaper to run the more you go fishin.
Reg,
JON