Re: 115hp from a 90hp Evinrude????????
It can be done. I'm sure you've read all the posts about crankshaft rated vs. prop shaft ratings. All that aside here are a few things to keep in mind. No matter what year cross flow you are talking about they both have the same bore and stroke, same intake and reeds, same ignition and same gear ratio. There are differences in the carbs and heads. The latest 115's have a different exhaust manifold. The biggest difference is the port timing. It is possible and fairly easy to port a 90 to 115 specs but you must have the motor completely apart.<br /><br />We have done this many times and the results depend largely on the boat's ability to respond to small increases in torque. It also depends on the set up of the 90. If it is poorly set up now and you make all these changes and set it up properly it may make a big improvement. The problem is that most of the gain was due to set up improvement. <br /><br />I would take a look at your current set up and make sure it's at optimum now. Let us know your speed (actual), RPMs, x dimention, water pressure, prop size, prop style and type of boat and we will calculate slip and see where you are now.<br /><br />Good luck!
