b89 Merc 115 4cyl 2stroke bad idle loss of power

"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"

A compression test is the firs

A compression test is the first thing to do in trouble shooting!-----Outboards are hard working machines and even a 20 year old machine can " look like new " but inside they are not like new. They are often run hot / wrong prop / poor oil etc etc. So do your self a favour with a compression test and a spark check to see if every cylinder has spark that will jump a gap of 7/16" or more.Stop spending time and money doing work that is not required--we see it so often " cleaned the carbs and the motor still runs the same"

A bad fuel pump will cause pro

A bad fuel pump will cause problems if the diaphram leaks into crankcase. (pinholes)

The hoses for the nozzles go in an endless loop back into the inlet of the pump so it can't develop enough pressure on that line by itself. ~4PSI is the max resuidal pressure. The #3 nozzle appears to be bad.