Originally Posted by Glaerox
3. Car (Fiat Panda 1.2 60HP, Pulls max 800KG (1750LB)
I used to own a Panda, and 800 kg behind one is a scary thought (even a newer presumably heavier one!). It would need to be a braked trailer - without brakes you'll be much more constrained. Braked trailer is going to add expense (and some weight to the package which then detracts from the boat options). It also adds an extra maintenance headache.
In terms of can it be done? then with a little compromise it might be possible... I suspect you'll struggle to get a "reputable"* brand of RIB, Engine and trailer that meets all your requirements exactly (including new within the budget) and gives you a reasonably fast package. The real question you need to ask is whether you can really hope to safely, comfortably and reliably tow 800 kg behind a 1.2L panda. I wouldn't.
However, don't be dispirited because you can get a boat that will meet your spec and may be nowhere near the upper weight limit you suggest. My boat is not technically a RIB (and so may be a little lighter?) but I am familiar with the numbers involved so I'll use it as an example:
3.9m boat .... 120 kg
'console' .... ~ 30 kg
20 HP 2str engine .... 48 kg (You can't get these new now)
Battery etc .... ~15 kg (You could live without)
Fuel .... ~ 30 kg
Anchor, and other "equipment" .... 15 kg
Trailer .... ~150 kg [IIRC] (this is for an UNbraked, bunk trailer)
So a total package weight of around 400-450 kg. And with a new price that is within your budget. If I was towing this behind a Panda I would probably still want a braked trailer even if it does manage to scrape through the technical unbraked limit.
* That is not to suggest that any boat which does meet the spec completely is not a good boat, or of reasonable quality - rather that the "big brands" in boats, engines and trailers attract a bit of a premium which may or may not be justified!