Not sure off the top of my head what my boat and trailer weighs, it's a 6.2m with a 90hp on the back.
I used to tow it with a 1.6 Sportrak which was a bit on the small side and thus used to snake a bit under heavy braking and was a bit underpowered. It was however great in 4 wheel drive when retrieving the boat.
I now have a 1.8 petrol Freelander, it tows the boat really well, but seems to be a little light on the front, have to be gentle on the clutch and accelerator when retrieving, not only with me either it seems.
When I was looking for the car did some searches on Google and the general concensus was that the 1.8 was a little underpowered, would not disagree with that though to me it is not a big deal.
Hope this is of help.