The ornamental design for a pontoon of a boat, as shown and described.
FIG. 1 is a perspective view of the pontoon of a boat showing my new design;
FIG. 2 is a partial perspective view of the pontoon of FIG. 1;
FIG. 3 is a front view of the pontoon of FIG. 1;
FIG. 4 is a partial top plan view of the pontoon of FIG. 2;
FIG. 5 is a partial side elevational view of the pontoon of FIG. 2; and,
FIG. 6 is a partial bottom plan view of the pontoon of FIG. 2.
The broken lines immediately adjacent the shaded areas in FIG. 1 represent the bounds of the claim and all other broken lines are for illustrative purposes only. None of the broken lines form a part of the claimed design.