Mercury Loss of Fuel Prime

andriesb2

Recruit
Joined
Jun 18, 2013
Messages
2
Have a Mercury 40hp 2-stroke 2005 motor. Runs fine at full throttle. But when I stop and it sits for a while, have to re-prime with bulb. Also, after re-priming, if running at slow speeds, looses prime.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Mercury Loss of Fuel Prime

Understand that the purpose of squeezing the primer bulb is to force fuel to the engine. Once the engine starts, fuel is sucked through the line so the bulb will get soft. That is not indicative of a problem unless the ball is sucked flat. That indicates there is an obstruction between the bulb and the pickup tube in the tank. That said, you said it looses prime at slow speeds. So what happens when this "loosing prime occurs"?
 

andriesb2

Recruit
Joined
Jun 18, 2013
Messages
2
Re: Mercury Loss of Fuel Prime

At slow speed, loose prime and the motor dies. I reprime by squeezing the bulb which feels to be full of air.
 

gpfishingdude

Chief Petty Officer
Joined
May 1, 2012
Messages
538
Re: Mercury Loss of Fuel Prime

At slow speed, loose prime and the motor dies. I reprime by squeezing the bulb which feels to be full of air.
Check your compression and spark. Mine did that and when I checked for spark I found that I had a bad coil. After getting it firing on all of the cylinders and tuning the idle mixture and idle speed it keeps it's prime now. I thought that mine had a weak fuel pump for awhile but it wasn't running right so it wasn't sucking the fuel properly.
 
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