Zeta:
I think that you can improve your speed a bit with prop tuning, but maybe not.
First it looks like you require about 90 hp to hit 8 kts, your hull speed. A good rule of thumb (oft quoted by yours truly as well as FF on this forum) is that it takes 15 hp/10,000 lbs (or 3 hp per ton) to move a displacement hull at hull speed. Given your weight of 52,000 lbs. (is that loaded?) then that suggests 78 hp.
So your 90 hp is a little high, but well within the range of full displacement passagemakers noted in the Bebe/Leishman book.
I would first get a copy of Dave Gerr's Propeller Handbook. Read it and then you will be able to understand (and challenge) any recommendations given by a prop shop.
But recognize that we are talking about marginal improvements. Your speed target of 7 kts is going to take about 40 hp. Your Volvo probably makes 17 hp per gph at that rate. So your burn target is 2.4 gph. You are currently burning 15% more than average. If you can get back to average that is a saving of 0.3 gph or a little more than a buck an hour. It will take a lot of cruising to pay for a new prop.
And contrary to other advice on this thread, I don't think that you can improve fuel consumption by overpropping or that you should. The 40 hp noted above probably comes at 1,400-1,500 rpm which is right in the middle of the sweet spot for specific fuel consumption. And if you ever need all of your available hp to buck a headwind, you won't have it and may damage your engine by trying.
David