mercury bottom carb blowing out

[sambrigman]

1995 40hp 4cyl mercury running rough bottom carb is blowing out while motor is running I can cover carb with my hand and makes no difference in running. would it be compression blowing out? any suggestion or idea greatly appreciated. thanks

 

[merc850]

Now that sounds like a stuck/broken reed valve(s).

 

[harringtondav]

^^+1 Also my thoughts.

 

[sambrigman]

could the reeds be behind the carbs? Or hard to get to?

 

[racerone]

On a 4 cylinder they are internal on the crankshaft I believe.-------Your serial # is ?-----Not easy for a novice.to fix-------But there are other checks to do first !!!------Compression first.----Then check for spark on each lead and see if it jumps a 3/8" gap.-------Sounds like the bottom carb is flooding.--------The reeds are very reliable but could be held open by seagull feathers I suppose.

 

[sambrigman]

serial # og140424 model #40elpto thanks

 

[DeepCMark58A]

If compression is good pull the carb bowls and clean them out, clean the floats. I had the same issue and it was a chuck of junk in the bowl.

 

[sambrigman]

1995 40hp mercury 4 cyl fuel pump not pumping reed valves??

This motor is driving me crazy. Bottom carb blowing out. I can cover completely makes no difference .I have tried all suggestions except reed valves, and now I find that the fuel pump is not working. I replace the pump, still not working. So could the pump not pumping be a symptom of reed valves. Thank you guys for your tips and ideas I am at wits end

 

[racerone]

I believe in inspection / trouble shooting.-----Did you take the old pump apart or did you just run out and spend $ and find that motor still does not work.----Sounds like you now have a good spare pump.-------With a bad reed valve you would not get crankcase compression, thus no pressure pulse to drive the pump.

 

[sambrigman]

So reed valves should be the problem? thanks

 

[DeepCMark58A]

Did you replace the check valves in the pump as well?

 

[sambrigman]

I got a new pump, and had the old one inspected by a mechanic, the old pump was good too

 

[GA_Boater]

Let's keep this all together in one thread.