exhaust

[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?

[HavasuDreamin']

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.

[TIMEBOMB]

I have done the same thing HD had done. I pulled the liner took a 1/2 drill bit down to a friends machine shop, fabbed up a 24 inch extension and welded the bit and extension together. Either get a drill stop or use tape, and attach it to the bit about 3/8 of an inch from the point. That way you don't drill start the cavitation plate when the bit goes thru. I went up in main jets .02 and left the transition jets alone. Now I run a offshore efi motor so none of the above applies. Later, Gary.
[ April 15, 2003, 12:34 PM: Message edited by: TIMEBOMB ]

[snappertapper]

i dont know if yamaha has an exhaust liner but i dont think i need to rejet my carbs either