(b) Use.— Dealer registrations may be used on any boat owned or in possession of a dealer, manufacturer or jobber and operated by the dealer, manufacturer or jobber or their employees only when the boat is used for any of the following purposes:

1. (1) In the business of the registrant as a dealer, manufacturer or jobber.
2. (2) For the personal pleasure or use of the dealer, manufacturer, jobber, members of his immediate family and regular employees thereof and members of their immediate families.
3. (3) For testing or demonstrating boats in the possession of the dealer, manufacturer or jobber.
4. (4) For lending boats to customers whose boats are being repaired.
5. (5) For lending to prospective buyers for a period not exceeding two days for purposes of demonstrating the boats.