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Mariner 40hp Marathon

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A.Merrill

New member
On the lake motor will start and idle good and will open up to 1/4 throttle then bogs down and dies. You can pump the prime button and get a little more out of it, but not much. At home with muffs on it, it will open up to full throttle but slows down then speeds up slows down and speeds up. Sounds like it's not getting enough gas. Carburetor has been taken apart and cleaned twice with no improvement. Could it be timing is off? I've never messed with timing and not sure how to set it on a outboard. Compression on top cylinder is 100 and 125 on bottom cylinder. This motor set for years and the top cylinder was 90 pounds and after being ran a little came up to 100 pounds, I'm hoping it will improve some more.
I can not find a year on the motor. One small sticker say Mercury marine serial number OG070785.
Mariner 40hp Marathon. Any help or ideas will be appreciated. Al
 
Clean the carburetor ( simple job ) as it might be gummed up from sitting with fuel in it.-----Test run with another fuel tank and hose.------The difference in compression does not bode well.----Not a timing issue !
 
racerone said:
Clean the carburetor ( simple job ) as it might be gummed up from sitting with fuel in it.-----Test run with another fuel tank and hose.------The difference in compression does not bode well.----Not a timing issue !
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Thank you for your reply. Carburetor has been cleaned twice, rebuilt fuel pump and news reeds. It's doing better it will idle for a few minutes before dying. It will open to half throttle start chugging and die. ??? Possible air in fuel lines ? I appreciate any help. Al
 
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