Dr Ruth, what would cause a 49 year old man to remain erect for hours only to have a problem with orgasm? 

The condition you describe is called priapism, and while it can happen to a man for no reason, it is very rare. Do you know whether he’s taken some sort of drug, like Viagra, or used a mechanical device, like a pump, in order to get his erection? If that were the case, it would make more sense. If this continues, and especially if there is no outside cause, he should definitely go to see a urologist.