I have a 2004 tahoe q7 with a 5.0 ,350 ,mercruiser alpha 1, 220HP with a mercury vengeance 19p prop. At full speed(cell gps) 44mph and the rmp are @ 3k. My lake Elevation is 6,600 feet. If I put a 17pitch will I get the RPM to 4,500?.Can I use it or this unsafe for the engine? On top of motor it...