Sunseeker Superhawk 48

What is broken exactly?
Those trim tabs are the so-called "K-planes" from Mercury Racing, and they are typically fitted in boats even faster than yours - much faster, in fact.
Very reliable and effective, and also simple in terms of controls, since all they require is a 1-0-1 flip switch on each side.
My guess is that the hydraulic pump is either shot, or badly connected. Either way, it's a rather easy fix.
As CR suggested, any Mercury dealer should be able to help.
Even better if it's a Mercury Racing dealer, which surely has seen plenty of them.

In any case, I wouldn't even think to replace them, because trim tabs don't get any better.
And you don't have enough space to fit wide enough interceptors, which I've yet to see in any performance boat anyway.
BTW, K-planes also give a razor accurate visualization of their position at the helm, through a mechanical cable with no electronic sensors at all, as in most other toy trim tabs.

For the records, I'm saying this not just based on general knowledge, but also because I used to own a Fountain fitted with the very same stuff.
And they were amazing, to the point that the only problem I had was to get used to light touches on their controls, due to how highly effective and reactive they were. The boat could actually be steered with the trim tabs alone!