Hello 27fever, We did 2 procharger Kits, a 29' fountain with a HP 500, and a 29' fountain with a 502 EFI. We got a 17 MPH with the HP 500, and a 20 MPH gain with the 29' 502 EFI. Both at a mild 3.5-5.0 lbs boost. The 502 is the most reliable engine for boosting. The internal parts are high quality, and it comes stock with a low compresion of 8.75:1. Both boats have over 400hrs of trouble free boating. hopes that helps. Regards, Claude of C & B Marine, any questions you can Email at, Kinkykanook@Mediaone.net