B-24 supercharger inop?

[stugumby]

Just curious as it seems you can select the supercharger in controls and apply the key but there is no message to hud or increase on the manifold pressure gage etc. from a b24 flight manual there is also a question regarding cruise, manifold pressure at 33 inches and 2350 rpm as a continiuos rating. cruise speed then is about 180mph IAS?? AOI can keep this pace but i cant at 7000m Im able to go about 150mph IAS. Anyone else have any data or tips to share??