This is for the engineers on here…without getting into over my head details a simple explanation will do. Dealing with a jet pump for a jet boat. This is an aftermarket one:
http://www.4-tecperformance.com/images/rr4951.JPG
The vanes around the nose cone on the stock pump have a rough cast finish to them, if they were sanded and polished smooth would that have any noticeable change in flow of water through the pump? The engine revs over 7,000 rpm at wot so it’s pushing a lot of water through it. I’m imagining it would be an undetectable difference while riding it, but then again there are other minor changes that can be made which suprised me as well.