When the prop is tilted forwards does this stop the front end digging in ?

thanks Johnny

Johnny,
I wouldn't say that it would stop it, but it should reduce the possibility. Depends on a lot of things, balance of the boat, where the prop is in that relation, and so on. Pushing the back end of a boat down tends to push the front end up, sort of... It's not a complete 'cure'.
- 'Doc

(Push the back end of one of my boats down and the @#$ thing'll sink!)

Ok ... kinda basically saying the same thing as above :

If you have your engine mounted more towards the transom ( rear ) area , then angling the prop downwards , will cause the front of the boat to be lifted , BUT , only due to the fact that the prop is literally forcing the rear ( transom ) area down . So ... pending on how heavy your front ( bow ) of your boat is , will depend on how much it will raise upwards .

Doc and Bob are correct with the answer for your question.
The main reasons why the bow digs in.
1. Too heavy on the bow
2. Not enough Bottom rake
3. Not a smooth transition from rake to bottom
4. Not enough power to get the boat to plane
5. Not enough bottom surface
6. The bottom may have a curve upward
7. Engine to for forward
With the airboats, the thrust that makes the boat move is located well above the bottom of the boat, connected by the engine stand. Basicly, no matter how the engine is position it will still have down force on the bow. The only real advantage of tilting the engine is if you tilt it so that direction of air blowing off of the props is in a downward direction. This is only to aid in getting the boat on plane, to put a little extra force on the bow, and it helps in making the boat slide around turns.
With the thrust point so high, it acts as a lever that multiplys the force on the bow.