2000 mercury 40 hp 2cyl bogs and dies

[kevin11mic]

I reacently bought this motor and it ran great when i first bought it. i took it out the other day and it started runing funny so i got it back to the ramp. brought it home and ran it on the hose and i couldnt keep it running. i played with the idle adjustment screw in all different positions but nothing worked. so i rebuilt the fuel pump and the carb. low and behold it is still doing it. it will crank then run for about 10 seconds then die. no matter what i set the carb at. any ideas before i goany further?

 

[oldman570]

Re: 2000 mercury 40 hp 2cyl bogs and dies

You need to check the vent on the fuel tank to be sure it is not pluged. Just loosen the fuel cap and try running it. Check any an all fuel filters for dirt or brown slime. Would be best to replace them. Run a compression test of the motor. Set the idle jets at 1 & 1/2 turns out from lightly seated. Replace the fuel hose from the carb to the pump with a clear hose and watch the fuel flow for air bubbles or bad fuel flow. Doing these test will tell if the fuel system is causing your trouble. Did you replace the fuel hoses on the motor with ethenol resistant hoses? Older rubber hoses will brake down and flak off and plug the carb again. Recheck the float levels of the carbs to be sure they are not set to low causeing the carbs not to fill as needed. If the gas was old you need to use fresh gas. JMO
Oldman570

 

[kevin11mic]

Re: 2000 mercury 40 hp 2cyl bogs and dies

The tank is one of the new ventless ones for emissions...il check all the hoses but the motor is very low hours so I wouldn't think that is an issue...the float has plastic rests so there's no way to set it. At the tank I have a Johnson fuel connector and a mercury one at the motor...I wouldn't think that could cause any issues only reason it's like that is because my old motor was a Johnson....I haven't done a compression test and I hope that isn't the problem...what should it read when I do it? It seems to me like the float is stuck because it only runs for 10 seconds and then dies...I just rebuilt the carb but it may not be fixed.

 

[oldman570]

Re: 2000 mercury 40 hp 2cyl bogs and dies

You should try using a vented tank and run the motor to see if that is the trouble. The last time I have seen a non vented tank was back in the 50's when they were used on the OMC motors. The compression readings need to be taken with the motor in the WOT position with the motor warmed up first. They should be over 100 lbs. and not be more than a 10% diffrence of one another. The fuel conectors should not make any differance as long as they seal up and not have a air leak. This is why I use a clear fuel hose, for testing the fuel system, between the pump and carb. If any bubbles appear in it , you have a bad conection some where from there back to the tank. All the carb floats I have used, even the plastic ones, still have some way of setting the float leavel, and you could ha a stuck inlet needle in the carb being that the motor only runs for that short of time.
Oldman570

 

[kevin11mic]

Re: 2000 mercury 40 hp 2cyl bogs and dies

Well went out there today and started it up after I had sat about a day...hooked up the fuel and it started right up and ran on the hose for about 20 min and never died...I played with the throttle quite a bit and turned it on and off several times...seemed to be ok...il know for sure when I take it to the lake...Maybe it was vapor locked??? Or I noticed that this motor has an in line check valve so when the fuel system gets over 2psi it won't let the fuel through...who knows ...I also pumped out about the first gallon of fuel in the tank incase there was any water in the bottom...

 

[oldman570]

Re: 2000 mercury 40 hp 2cyl bogs and dies

It could have been water in the tank being that you pumped out some. At least it is running again and a lake test should tell if that trouble is fixed. Anytime you run a motor on muffs there are a couple things that you should remmber, 1=never rev the motor very high RPM's as there is no backpressure on the motor and it could over rev and cause alot of damage, 2= because there is no backpressure the motor will act alot diffrent in the water and not rev as hight as it dose on muffs, 3= never set the final carb setting untill the motor is on the water and in FWD gear. Setting the carbs any other way could cause a lean burn and can cause the pistons the burn up the tops. It is a good practics to run the motor for a short time and then pull the plugs and check them and the pistons to see if the settings are correct.
I've never realy noticed any check valve in the gas feed system as the carb floats and inlet needls are designed to elinate that trouble. I would have to see the system inorder to understand just why it is there. The only check valve that is in the fuel system that I know of is one in the oil feed to the fuel punp on the oil injection system. It is there to keep the oil from being pushed back to the oil pump and keep the oil pushed into the fuel pump so the motor gets the oil needed to lube the motor. If this is the one you are refering to then it is correct and should never be removed. JMO
Oldman570