Our 150 four stroke is very closely related to the 150 ProXS, which makes 5 more HP, at 200 more RPM. The Pro version also has a 4.88 gearcase with low water pickup, which is attractive on its own. But, when you do the math, the gear ratio difference really makes the ProXS a difficult proposition. It's a great engine, the 4 cylinder single overhead cam, but that extra 5 HP is lost with the 2.08 gear ratio found on the Pro. Effectively, you nullify the advantages of the higher rev limiter, by gearing down.