Kevin is right on the mark. The Nitro case is 1.86:1 ratio, so you will not over rev props. There are some 2.42:1 Nitro cases used on the OMC, 2 Cyl. motors around 50-60 HP. You of course, do not want the 2.42:1 ratio. We ran the Nitro and SST-60 cases quite high on tunnel boats in SE & SST-60 class without problems. Also, there are heavy duty rear bearing carriers available for same. We suggest pinning the carrier in either event. Please, forget the bigger V-4 case. It will only disappoint you.