I've got a few faulty Volvo Penta actuators, not sure if they are the same type as yours, but these consist of a leadscrew driven by a small motor. In the other end there is a feedback potmeter. What seemed to have happended was that, probably due to bad stroke adjustment in the controller, the nut part of the leadscrew assembly "bottomed out" and got stuck. Once I manually reversed the screws most of them ran fine. These were replaced under warranty and were due to be discarded but somehow ended up in my basement
If VP will not fix it under warranty, I can post a few pictures...
reparere, kalibrere, konfigurere, destruere, protestere..."
- Pompel...eller Pilt ... eller http://geirmeister.net/gorgon.mp3
Gorgon vaktmester ... eller Geir