1986 90hp Tower of Power Cylinder 3 no fuel

[tmfeaster]

I have a 1986 Mercury 90hp Tower of Power Outboard.

Cylinders 3 and 4 run off the middle carb. Cylinder 3 is getting minimal gas and looks very dry through the spark plug hole compared to the other cylinders.

Carbs have been taken off and cleaned. Compression checks all good in all cylinders.

Noticed this because last time out it started losing power to get on plane.

Any ideas? I did notice carbon on the plug when I pulled it.

I have replaced all 6 plugs with NGK BUH8 since the last time out but haven't ran it with the new plugs. Scared to run it until I know that cylinder is getting fuel.

 

[racerone]

I guess it would have to be an issue with the reed valves.-----Perhaps one is broken / stuck open by debris.-----Looked for holes in the crankcase ?

 

[Chris1956]

Bad reed valves would be unusual. Cyl 3 would normally get a little less fuel than cyl 4 due to gravity effect on fuel. I would check float height and drop and clean out idle and main jets on middle carb.. When you pull off the carb, you may be able to see the reed valves, with a small flashlight.

You have spark on all 6?

 

[racerone]

Boost venturi in one piece and in place in middle carburetor ?

 

[Faztbullet]

Cyl 3 would normally get a little less fuel than cyl 4 due to gravity effect on fuel

Bovine Scatology as gravity has NO effect on a atomized fuel charge...if so clouds couldn't stay in the sky.:facepalm:

 

[racerone]

Learned a new term / description today.------Thanks for posting that.-----Just too many " old wives tales " out there !

 

[Chris1956]

Hey Fazt, gravity affects light, yet it still shines across great distances. Your statement is patently incorrect.

In this case, not all fuel is atomized to the same extent. Larger droplets of fuel are affected more than finer droplets. Some of the larger droplets are burned in the lower cylinder pair, causing it to run a bit richer.

 

[Faztbullet]

No...its your statement is patently incorrect.

In this case, not all fuel is atomized to the same extent.

WRONG as fuel exits a metering tube in a carb and atomizied as it is introduced into venture. Atomization is the same no matter the RPM as the only thing that changes is volume. Almost as bad as saying rear cylinders on your V-8 truck runs rich cause it is going forward.

gravity affects light, yet it still shines across great distances.

Only effected by gravity of black holes not by gravity here on earth.

 

[Chris1956]

Gravity on earth is less than gravity of black hole, so it has less effect on everything, including clouds and light. However, it has some effect on everything, including carboration.

BTW - clouds stay in the sky because they are less dense then the air under them, not because gravity does not affect them.

 

[Faztbullet]

No again.. the water droplets are so small that the effect of gravity on them is negligible and atomized gasoline is lighter than water so your theory is incorrect. Any droplets that would be large enough for gravity to effect would cause running issues as a spark will not ignite raw fuel in a cylinder. The only way your theory is 1/2 correct is if engine is missing bleed restrictors and puddled fuel is running into cylinder below it.
FIN
Die Ende

 

[tmfeaster]

Got it figured out. Tilted the motor up and poorer an entire can of seafoam in it. Problem solved...whatever was blocking fuel is no longer an issue.

Now a new problem. I keep fouling the top 3 plugs with carbon deposits on them.