The yard reported that they tried a couple of smaller props, and the boat was able to get to max rpms and hull speed without the black smoke. My friend purchased the boat and we delivered it yesterday. Over the winter storage he will have the prop sent out to make sure it is pitched as stamped, and will replace it or re-pitch as needed. The yard did pull the exhaust elbow and said that while it had some minor soot it was not plugged, although from all the comments it seems taking it to be boiled out may not be a bad precaution. The odd thing was that the boat would make max rpms in reverse, just not in forward. We suspected the prop initially, but the year decided to pursue many other avenues before checking the prop :/

Thanks for the comments!