Big Block engine build?

[Jetlink]

Hull design might be your stumbling area. Not sure how the hull looks on yours but as you get going faster, the stern wants to lift and shove the bow down on my boat.

[cadunkle]

Yes, be careful as you approach 60 MPH. It can get hairy on inboards with a steep shaft angle like ours. Pushing the bow further down at higher speeds can have a tendency to catch the bow and pull hard one way or the other.