which i know can reach 50mph
but i was struggling to get 40mph out of her and was cavitating bad
with a little water also being sprayed upward.

The trim gauge doesn't work either,but,knowing that the leg is down
and a standing full throttle start,after several seconds i start to
slowly raise the leg and before i know it,its cavitating and have to
close the throttle again.

If you have been getting 50mph, but are now getting 40mph, then the most
likely thing that has changed is that you have bent the aluminum(standard)
prop by hitting a sandbar...assuming that you aren't trimming up too high
now. A bent prop can reduce the prop pitch and/or cause
ventilation/cavitation).

Knowing what your trim angle is would help you for maximizing and repeating
the proper angle that you determine for best trim, so getting that fixed
would be nice.

If you can't get rid of the ventilation by fixing the prop, or getting a new
stainless one that won't bend every time you hit a sandbar, then you can get
a hydrofoil mounted on the outdrive. I have a mercruiser 4.3/alpha one and
the hydrofoil completely eliminated the ventilation I was getting.