Whaler,
Hope that Charles fix is the problem. If not then you could have a starter whose windings have become heat sensitive over a period of time and some of the insulation could be breaking down allowing loss of tourque when hot. If the timing fix doesn't help, try an old known good starter if it isn't to big of a job to change them out. I fought that for almost 3 months in my 428 until I finally put in an old starter that I had laying around and that cured it. I then went out and bought a new starter and have had no problems since.
Ron
