The ornamental design for a boatbow, as shown and described.
FIG. 1 is a front, top perspective view of a boat bow according to our new design;
FIG. 2 is another front, top perspective view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a front, bottom perspective view thereof;
FIG. 6 is another front, bottom perspective view thereof;
FIG. 7 is a side view thereof; and,
FIG. 8 is another side view thereof.
The broken line showing of portions of a boat is included for the purpose of illustrating environmental structure and forms no part of the claimed design.