The second boat has a mass of 2670 kg.
You know that force is equal to mass multiplied by acceleration.
Notice that, compared with the acceleration of the first boat, the acceleration of the second boat dropped significantly.
Since the force acting on the two boats is unchanged, this implies that the mass of the second boat must be significantly bigger than the mass of the first boat.
Mathematically, you can write
Since the same force acts on both boats, you can also write
As a result, you have
Solve this equation for
Rounded to three sig figs, the answer will be