Gary Coffman wrote:

Unless the boat and block are in different gravitational fields, the
result is the same. W=mg.

No. 'W' is a force. 'M' is the measure of inertia of a body.
'W' is vector, 'M' is scalar. They aren't the same.

Re-read my post. I did not say weight and mass are the same. I said
the _result_ was the same. Indeed, mass is a scalar and, in a uniform
gravitational field, g is a vector thus so is W. However, under
appropriate circumstances, g may be a tensor.

Ted