Stabilizing isn't as easy here as it is O/S. For the outside rotten bits I'd suggest painting on a few layers of wood hardner, available from Bunnies or similar, but not cheap. It is a thin watery milky product that turns hard and clear as it goes off.
For the inside, looks like a hollow, so I'd fill with either clear casting resin, or the same mixed with black tint.
Hope this helps
__________________ Neil ____________________________________________ Every day presents an opportunity to learn something new | 
stabilising redgum 
