I have a 1995 Boston Whaler 15' Rage Jetboat with 115 OMC engine. I
came across an interesting posting on the Boston Whaler forum about
adding a "stuffer" prop to pre-feed the impeller to boost performance.
I've linked to the document here
http://www.geocities.com/cms_30338/Stufferprop.doc

Anyone done something like this and seen an improvement? Any
problems?