Ok I am rebuilding my powerhead (new rings and complete gasket set) on my Evinrude 15hp. Since I have it completely apart I am wondering what kind of gains I would see from boring it out? (they make .20, .30, and .40 over bore) Is this worth looking in to or just a complete waste? We used to bore out our dirtbikes back in the day and saw huge gains! But a boat engine?