I have recently purchased a 95 sea ray 180 signature with a 4.3L mercruiser and an alpha one drive and the gear ratio is 1.5 my elevation is about 5000ft, im not to sure how gear ratio works but I’m not hitting my WOT I currently have a14.25x 19 P the boat came with but it’s in rough shape and my wot is about 3100 rpm at 25-30 mph according to my speedometer not gps. I only have put the boat out in the lake once and would like to have correct prop. I’m not to worried about top speed I mainly just use it for tubes and wake-boarding any info would be helpful. Thanks