snappertapper:
doin a little expiriementing on my 150 yayama, its goin on my hydrostream when its done, how do i cut/drill exhaust holes, and what else do i need to do? All I can do is tell you what was done to mine. I have either five or six (I forget) holes about 3/8" or 1/2" diameter drilled on both the right and left side of the midsection immediately above the gearcase. Mercury motor's come with exhaust liners .........mine was removed. I didn't open mine up, it was done by Dick Sherrer Marine several years back. That is all I know.
Do you have to rejet your carbs if you go from an unopen exhaust to a relieved system?? Just curious.