yes,these will fit 15 spline mercruiser alpha one and large gearcase merc outbourds.i fit these on my baja with alpha one and they fit fine.i had these for my yamaha 175 and i called propusion inc. over in hudson(well known here on site) and asked if i could run these on a alpha one and the man i spoke with said yes that they would work fine and fit.if you have intrest you can call me at 608-863-5045.i can find out what shipping would be to pella ia.will have to take to post office and have them scaled for cost.these props are in like new condition with box.