Seems high for a 150, but the -32 carb does have a WOT enrichment circuit, so I would expect it to be a bit rich. Did you build this plane? Many drill their main jets to overcome a lean condition during some WOT phases. I suspect some may think "if a little is good, more is better." That would leave you very rich. I have a 160 and when it had a carb, I drilled the jet, but never burned more than 14 GPH in any phase of flight.
I would not consider this to be a too big of a deal, though it would be nice to be able to trust it with the red knob full in. The Lycomings are always very rich and you'll want to get used to leaning in most phases of flight. I have FI and an FP prop. I routinely lean a bit at take-off, as it is too rich with the prop spinning 2300. As it moves up to 2500 I have to richening it back a bit. The overly rich condition was impacting my initial climb performance. It is still running 150+ ROP. That gives me much better power and I have no issues with cooling.
These carbs are very old designs and pretty unsophisticated. Further, they are set up to err on the rich side of anything, so you will find some power settings worse than others.
Learn what your peak EGTs are at various RPMs and just lean to 150-200 ROP in high load situations and best power (80-100) in others or LOP.
EDIT: 16.5 at 2500 is at least 3 GPH high for a 150 maybe more, so I would expect something is going on in your carb or with your fuel flow sender. You'll want to address this relatively soon. As the hot weather gets here, engines need less fuel. At some point you run the risk of your engine sputtering at the DE of the runway because its too rich. I would be leaning on take off and getting the flow down to around 13 or so to avoid problems, assuming you have verified the accuracy of your fuel flow device. You should be able to easily index your Mixture shaft with the proper point.
There are several things that can cause this, but high on my list would be a leak somewhere (should be easy to spot that much leakage) or debris in your needle/seat or saturated float. I have seen other report bowl screws that loosened causing problems (an easy visual check).
Larry