What size engine would it take to tow 2.5k (boat)?
25000 lbs boat is meant to be hauled by a semi truck with a boat trailer designed for a boat of that style. Now if you meant a 2500 pound boat a small V8 and some of the more powerful V6's would pull it nicely, but it largely depends on the trailer tongue weight and the hitch that is attached to the tow rig and if the trailer has brakes.
You need to add the trailer weight to the boat weight to get the gross weight. Then refer to the owner's manual to see if your vehicle can safely tow the load. Any V-8 and most V-6 engines could tow 2,500 lbs easily depending on tongue weight and the tow vehicle's capabilities.
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