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Jeremy R.
Jeremy R., MarineTechnician
Category: Boat
Satisfied Customers: 9020
Experience:  Multiple factory certifications 20+ years of experience.
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2005 40hp outboard Mercury engine I had contaminated fuel

Resolved Question:

2005 40hp outboard Mercury engine: I had contaminated fuel trouble. I replaced the filter, rebuilt the fuel pump, cleaned the carburetor and made sure the entire fuel system was clean. It will fire initially for two or three hits and then will not fire again. With repeated cranking, raw fuel come out the exhaust. After sitting several hours, I can repeat this same result.
Submitted: 7 years ago.
Category: Boat
Expert:  Jeremy R. replied 7 years ago.
Welcome to JA

sounds like you did not set the float in the carb right or the fuel pump might be bad

I always rebuild the carbs when i clean them and always replace the fuel pump also
Customer: replied 7 years ago.
I did rebuild the fuel pump. The carburetor looked so good after I cleaned it that I decided to go with it because the engine had been running very well before the contaminated fuel got in. This engine is in perfect condition and I suspect that the contaminated fuel cleanout/cleanup somehow caused the problem.
Because it was running before the contaminated fuel, do you agree that I should focus on the fuel system?
How do you set the carburetor float?
What troubleshooting procedures would you do?
What tests should be done for this situation?
Given the situation, are there any other things that might cause this problem?
I bought the Clymer Mercury repair manual but it does not give enough details on how to test and troubleshoot the fuel system.
I'm in a rural area that has no marine repair services.
Give me whatever you can to methodically isolate the problem.
Customer: replied 7 years ago.
I need more detail. Read my reply!
Expert:  Jeremy R. replied 7 years ago.
yes the carb needs to be cleaned very very good

i spray carb cleaner in every hole then use compressed air to blow out

the float in the carb is set to level when the carb is on its side

you want the factory manual for this, not an aftermarket one
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