The key is asking yourself have you presented with something he can act upon.
My experience as an investor and someone who has sought out investors is that if they are busy and vaguely interested they might keep you on their todo list but it will stay 10th to 20th thing to do today.
The only way to move is to create a decision or action point, only then does it move in the top three and has a chance of being effected today.
Many companies come to me and ask me to sell myself on the project by defining this and that and proposing this and that option. This is lazy and unhelpful as I have like many other people many tasks I need to do and want something that is easy to make a decision on or refine if I am not happy with it.
So my advice have a clear action, decision that he needs to take and take it to him, do not ask him to do the thinking, if he goes along and make the appropriate decision then he is interested if not then it is a clear sign to go elsewhere.
You cannot stay in this riskless, unproductive stage of interest, just like in sales you have to give him a chance to actually buy something tangible