The ornamental design for a boatfenderstrap, as shown and described.
FIG. 1 shows a frontal elevational view of my boat fender strap design, the
broken lines showing a portion of a boat bumper 10 are for environmental
purposes only, and do not form part of my design; and,
FIG. 2 shows a rear elevational view of my boat fender strap design; the
broken lines showing a portion of a boat bumper are for environmental
purposes only, and do not form part of my design.