I have a 1977 115 Evinrude that I would like to try and get somemore power out of. I have already done the following to the motor as far as upgrades: 135 heads (155 psi compression across the board), 135 carbs, 135 exhaust (block was not cut out for it though), bored .030" over with a set of wiesco pistons. With the help of Dhadley I have improved my setup and the boat responded really well to the changes. I'm running a OMC 19" SST prop that has been trued and reworked to factory specs. I was only turning about 4800-4900 rpms before and since I raised the motor I've turning around 5300. <br /><br />I hear all the time where people are turning these motors 6500+ and I just can't figure out how they are doing it. With my boat design, I'm about as high as I can go with my motor height. I can go to a smaller pitch prop and gain rpm's but I loose alot of speed i the process. <br /><br />I guess my question is, what are some performance upgrades I can do to the motor to gain more rpm's? I don't want to tear the whole motor down again just yet, I'm mainly talking about intake mods, exhaust mods, etc, etc.<br /><br />Dhadley.....I know you said to let's get my setup optimzed first but, I think I'm as good as I can get. Can you tell me more about the plenum intake?<br /><br />Thanks again:<br />Jason
