I never paid a fee for any boat that I sea trialed.

You're correct in the case of an acutal sea trial. The seller furnishes fuel,
assumes the risk of damage to the vessel, etc.

This is a case of launching the boat to perform an engine survey:

Quote:

We've spoken to a marine surveyor we might
hire who says that the engine can be tested to some extent on land but
that we really should put the boat in the water and check it out.

If it's a survey expense, it's traditionally the buyer's responsibility.

Most buyers aren't going to be paying for an engine survey until they've had a
satisfactory sea trial. If the boat won't start or run for sea trial, it
doesn't take a mechanical genius to assess its general operating condition.
:-)