The ornamental design for a marinadeinjector, as shown and described.
FIG. 1 is a top perspective view of a marinade injector showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a right side elevational view thereof, the left side elevational view being a mirror image;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
Broken lines in FIGS. 1 to 3 and 5 show the bottom portion of the barrel of the marinade injector and the injector needle of the marinade injector, neither of which form part of the claimed design. The dot-dash-dot broken lines in FIGS. 1 to 3 that extend across the diameter of the barrel of the marinade injector form a boundary line representing the bounds of the claimed design.