Using my Flowscan, gps, fuel gauge and the basic fill up before and after, I am getting an average of 4mpg with a 150ETEC on my 20SF - cruises at 3800-4000 and 36-40 mph. I say this because I had a 175 carbed Yami - 1990 before I got the ETEC. Using the same methods, I got about 1.5 mpg with it on the same boat.