Sometimes you can hear the turbo on some engines -- and sometimes not. On a smaller one inside your engine room, I'm skeptical. You might, depending on the configuration be able to remove a cover and see if the turbo is spinning (but on you Volvo, it may not be in a place that's possible, and I'm not sure of the configuration of your turbocharger).

Usually, I would suspect that your engine would have the turbocharge kick-in before you get to 2800 rpm and you'd notice something not running right (fuel not getting burned and black soot discharge increasing in the exhaust, etc.).

If your prop ha some growth or you've picked-up a fishing line, you could just have dramatically limited your top end RPM's and efficiency of your system.