B
Bill F
Guest
"I have an '89 Mercury 115
"I have an '89 Mercury 115 4-cyl 2-stroke. The idle is very rough with lots of smoke.
So far I have tried:
1. Adjusting idle mix screws on carbs 1 & 2 didn't help.
2. Carb cleaner spray + liquid cleaner in fuel didn't help.
3. Suspecting perhaps a stuck float I dismantled & cleaned carbs. No particular crud or water found.
4. Rebuilt fuel pump. Didn't help, but now I have an additional problem: loss of power. Won't go above about 4100 rpm.
5. #3 spark plug gets VERY oily after just a few minutes running. Swapped plugs with other cylinders: still #3. All 4 cyl get hot spark when cranking.
My conclusion at this point: there seems to be an accelerator pump that squirts fuel into the transfer passage on carbs 3 & 4, with some sort of flow/backcheck device at the end of the hoses, right at the block, hiding behind the ignition module. I figure #3 is dirty/broken or whatever and is allowing too much fuel to flow through when it shouldn't. Rebuilding the main fuel pump made the problem worse because now it is putting out higher pressure, hence the loss of top end power; #3 is running 'WAY too rich.
Comments?
Thanks,
Bill"
"I have an '89 Mercury 115 4-cyl 2-stroke. The idle is very rough with lots of smoke.
So far I have tried:
1. Adjusting idle mix screws on carbs 1 & 2 didn't help.
2. Carb cleaner spray + liquid cleaner in fuel didn't help.
3. Suspecting perhaps a stuck float I dismantled & cleaned carbs. No particular crud or water found.
4. Rebuilt fuel pump. Didn't help, but now I have an additional problem: loss of power. Won't go above about 4100 rpm.
5. #3 spark plug gets VERY oily after just a few minutes running. Swapped plugs with other cylinders: still #3. All 4 cyl get hot spark when cranking.
My conclusion at this point: there seems to be an accelerator pump that squirts fuel into the transfer passage on carbs 3 & 4, with some sort of flow/backcheck device at the end of the hoses, right at the block, hiding behind the ignition module. I figure #3 is dirty/broken or whatever and is allowing too much fuel to flow through when it shouldn't. Rebuilding the main fuel pump made the problem worse because now it is putting out higher pressure, hence the loss of top end power; #3 is running 'WAY too rich.
Comments?
Thanks,
Bill"