The ornamental design for a rowingboat with removable hard cover, as shown and described.
1. Rowing boat with removable hard cover
1.1 : Perspective
1.2 : Perspective
1.3 : Front
1.4 : Back
1.5 : Top
1.6 : Bottom
1.7 : Left
Perspective view 1.1 shows a removable boat hard cover designed to be mounted on car roof racks for transportation of the boat; top view 1.5 shows the deck and aft part of the boat shaped like a swallow's tail; bottom view 1.6 shows the hull and V-shaped bow dividing into a double catamaran hull shape; the right side view is omitted because it is a mirror image of the left side view; the parts shown by means of broken lines in the reproductions are not part of the claimed design.