I have an 02 42' 575 lightning. Will be pulling the engines and upgrading heads, cams, pulleys, etc. for about 650HP. Was thinking of going to shorties and 5 blades. Anyone tried this? What were the gains? Any suggestions?

I don't have your answer, but maybe do a search on a 42 with 600 sci's I know a decent number have been produced, the set up and props would have to be very close to your end product.

I am in the same process. Imco said definately need 5 blades, i went 2" short with my XR uppers. Precision Marine is doing my dyno tuning and i upgraded to hydraulic roller over the flat tappet cams thru them. Added the 3.5 pulley last year and Mark did the ecu's , it ran great. This year should be better, i am freshing entire motor package