I have recently sold my boat and at the buyers request provided a sea trial however I only agree to a water test as the final step in the sale. By that I mean the final sell price was negotiated and agreed upon by both parties subject to the satisfactory sea trial and unless the sea trial discloses an issue, mechanical fault or other, then there would be no further negotiation and the sale would be finalised. The boat was sold and both the buyer and I were very satisfied.
Ross