Evinrude Sportwin Performance

[beatstheshore]

I have a 1969 evinrude sportwin 9.5. When they went to the 9.9 / 15, they changed out the high speed orifice from a .0XX to a .0XX.<br /><br />My 9.5 has an original .048 high speed orifice. Although they are different motors, doesn't it stand that I might be able to get a little more power with a bigger orifice? I changed up to a .060 (56% larger cross section) and the thing floods out before it reaches its high rpm. Just wondered if anyone has tinkered with this type of motor. I'm thinking I need a .055 (about 30% bigger)<br /><br />Please help.<br /><br />------------------<br />Bob Gibbons

 

[JB]

Re: Evinrude Sportwin Performance

Howdy, Beatstheshore. It seems that a lot of people are confused into thinking that more gas means more power. In 2 stroke engines often just the opposite is true. Optimum power is produced by an optimum mix of fuel and air. Once you have this mix, introducing more of either can reduce power, waste fuel, increase carbon buildup, increase smoke and stink and, ultimately, destroy an engine.<br /><br />Jet (orifice) size is optimized for an engine's displacement at sea level pressure and several subtle engineering features of that particular engine. Usually, they run an engine a little richer than is best for peak power in order to run it cooler and ensure lubrication.<br /><br />Go back to the original .048 jet. You are wasting fuel, adding carbon buildup and shortening the life of your engine. <br /><br />Unless you are prepared to squander lots of money and sacrifice your engine forget about hot rodding outboards. For the most part, they are as powerful as they can be and still retain flexibility and reliability.<br /><br />Red sky at night. . . . <br />JB