When considering a used Boston Whaler boat, I would specifically check for the following:
--integrity of the transom; look for any sign of water ingress; look for mechanical weakness in the transom by using the outboard gear case as a lever arm and exerting bending force to the transom;
--integrity of the hull bottom and all underwater surfaces; look for any indication of damage that resulted in a puncture or opening of the gel coat layer; if the hull has anti-fouling paint there may be repaired areas that are obscured by the paint; make a careful visual inspection;
--that all original components of the boat are present and intact; in particular the navigation lamps, railings, hatch covers, seats, console, and so on; these components are difficult to find and expensive to replace if they are missing;
--the general condition of the boat and how well it has been cared for; the gel coat layer should not be dull, oxidized, and cracked; it should be crack-free, have no wavy distortions, and have a nice lustre; there should be no top-coating of paint on the gel coat, except possibly anti-fouling paint on the hull bottom, which then should be properly applied and follow the natural waterline;
--the static water line of the boat; at rest the drains of the engine splash well should be just at the waterline or perhaps partially submerged; boats that sit with the transom splash well drains completely below the water line may have gained hull weight due to ingress of water or have too much weight in the stern (such as multiple engines, batteries, or other gear);
--the integrity and condition of the aluminum below-deck fuel tank; remove all the deck pry-out access plates and make a close visual inspection of the tank surfaces; a boat in good condition will have a fuel tank that retains the aluminum primer paint color (a green-gray), and the tank surface will be free from dirt, mold, and black gunk; check the fuel lines to be certain they clearly show they are tolerant of alcohol fuel; generally rubber fuel line made prior to c.1987 will not be alcohol-tolerant and must be replaced. Replacement is expensive and labor intensive.
Also see my article which will mention these points and a few others. See
Buying Classic Boston Whaler Boatshttp://continuouswave.com/whaler/reference/buying.htmlWhen considering a used outboard engine, see my remarks in a separate article:
Assessing Used Outboard Engineshttp://continuouswave.com/whaler/refere ... Check.htmlWhen considering a used trailer, I would specifically check for:
--current registration and licensing
--general condition of the frame, axles, springs and other major metal components
--required lighting, lamps, and associated wiring
--age and tread wear of tires
--lubrication and condition of wheel bearings