Im doing a rebuild on my spare powerhead. Its a 1990 evinrude 120 This was supposed to be done and then swapped with the one on my boat. The one on my boat let go on me saturday so now its time to get busy.

Im just checking to see if I can expect any reasonable gain before I put it back together.
I had the heads milled down .040 witch leaves me with a dome of .71 hight. I opened up all ports by 2 mm wide and made the boost ports about 1 mm deeper. I also opened up the reed cage just a bit. I didn't change the hight on anything.

Im not expecting much of a gain from the ports because I can't get down and open the channels without pulling the sleeves (not on this motor).
I am hopping to gain a bit in over all pull. I just want to be able to get out of the hole and run a reasonable speed in my 17' bass boat.