The ornamental design for a upperpartsunit for an outboard motor, as shown and described.
FIG. 1 is a right side, front perspective view of upper parts unit for an outboard motor showing my new design;
FIG. 2 is a left side, rear perspective view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom view thereof.
The broken line showing of a portion of an upper parts unit for an outboard motor is included for the purpose of illustrating environmental structure and forms no part of the claimed design.