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4 Cylinder Mercury Carbuerator Outboard running on only 2 cylinders

T

Tjotta

New member
Hello!

I recently bought a 2001 Mercury 50hp Four Stroke carbuerator engine. It ran fine for a while, but after i changed the fuel tank, some dirty gasoline found it's way into the engine and clogged the system. After cleaning the carbuerators, cleaning the fuel system, changing out the gas tank for a brand new one and chaning the hoses it finally started again.

However it runs just on 2 cylinders. Cylinder 1 and 4. I have checked spark on the two cylinders that are no running (Cyl 2 and 3) and the spark is good, but when i take out the sparkplugs they are completly dry. I can't for the life of me figure out why this is.

Please if anyone has a soulution for this it would be greatly appreciated! :)
 
Try pulling the vent hoses off the carbs. Black custom hose one piece that runs down the carbs and connects at top of carbs. And run it. If that doesn't work. Pull off the intake before the carbs. Place your hand lightly over the mouth of the carbs that aren't working while it's running . See if that excites them.
 
Thank you for answering!
Going to try what you suggested when i get home. I just want to ask you what you mean by «black custom one piece that runs down the carbs and vonnects at the top»
 
Its a hose with 4 other hoses attached to it. But its a one piece hose and it's black.
It connects all the carbs vents. In case of an overflow in the carbs. The fuel is dumped through the cowling at the front. And it's a vent line. If the vent gets plugged the carbs will not fill up with fuel. And the engine will starve and stall out.
 
I have tried what you suggested, the vent hoses are completly free and when i hold my hand over the carb gasoline starts to pour out of the vents.

Do you know what this means?
 
I just wanted you to slightly put your hand over the carb to create a richer mixture. To see if the carb is drawing fuel or not. Don't put your hand tight to the carbs or it will dump out fuel
 
..."it runs just on 2 cylinders. Cylinder 1 and 4"

That means it's NOT the carbs since 2 and 3 are attached to the same carbs.

Look for wiring issues.

Jeff
 
Then I would believe that 2 carbs are not working at idle. Low speed jet is plugged. Or low speed circuit is plugged. Tear down those 2 carbs and inspect the low speed jets. Plus make sure the float needle is not stuck also..
 
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