Gas coming out carb during cranking

1975 40HP evinrude (40554c)

The problems started last weekend with the engine not revving while at WOT. It ran great through about four gallons of gas then started giving me trouble. When set to WOT the engine acts like it is set to about 20%. We brought it in and placed it in a trashcan and can now see fuel running out of the carb (at the air intake) when trying to start it. In order to get it to start we have to go 1/2 throttle, choke until it fires then it will run stable at a low RPM without the choke.

I just put a fresh carb kit in it about one month ago (maybe 15-20 hours) and has run great until now.

Any help would be greatly apperciated, the summer is getting away from me fast

Re: Gas coming out carb during cranking

Raw gas running out the carb throats is common while choking, Do a compression , and ignition test.

Re: Gas coming out carb during cranking

Your float(s) are not sealing off once the carb is full of gas. I bet your buld wont get tight?

Get you a rebuild kit for all your carbs and soak then and rebuild. After soaking use compressed air the blow all thos small holes.

To see if you did the job right hook up your fuel line and pump the bulb up, it should hold tight. If not you should see gas pouring from a carb.


if your going to store gas....Treat the motor and the gas.

Re: Gas coming out carb during cranking

Thanks for the responses...

Randy how long should the bulb stay tight? I have noticed in the past after running it for a bit the bulb softens. What would I experience with this motor if the diaphragm was slightly stretched out. I took the fuel pump off today and it seemed as if the rubber might be a bit too stretched ...is this a possibility? A fuel pump kit was put in the carb 5 years ago, without treatment and has maybe 50 hours on it. Did the sitting all this time with the pressure from the springs take out the elasticiity in the diaphragm? If it was too stretched or even mildly stretched would it even run/pump fuel; what would be the symptoms of a worn diaphragm?

Re: Gas coming out carb during cranking

The primer bulb is a wide spot in the fuel line, fuel is being pulled through, not forced through, why would it stay firm? A fuel pressure test would give you the answer. 1-4 lbs. depending on RPM.

Re: Gas coming out carb during cranking

His statement: We brought it in and placed it in a trashcan and can now see fuel running out of the carb (at the air intake) when trying to start it.

It seems to me the pump is pumping. However, by checking the bulb with the carbs rebuilt, (motor not running) will tell him if his float(s) of said carb is sealing off.

I agree the primer bulb is nothing more then a wide spot in the line. But it does play a big role in getting fuel to the motor.

If you hold the bulb with the arrow pointed up it should pump tight as dicks hatband. If is doesn't ya got leaks somewhere.

Trouble shooting 101.

As far as you pump goes replace it if you feel it's needed. We are not talking alot of money here. Check the fuel pump pressure as the other guy says, if you have the stuff.

Check the simple things first, then find you a good mech.

Re: Gas coming out carb during cranking

It's a 1975, so it has choke plates and not a primer solenoid, therefore, the use of the choke may flood the engine, but should not cause fuel to flow back out of the carburetor.

The float valve needle should stop the flow of fuel once the float bowl is full and prevent the overflow. If it does not, the updated float needle spring clip may not have been installed, or the float may be set incorrectly.

Without the clip, the needle can more easily stick closed, causing the bowl and system to run out of fuel, or stick open and flood the carburetor.

Re: Gas coming out carb during cranking

if none of the other stuff works,it could be a broken reed

Re: Gas coming out carb during cranking

If the engine is tilted slighty forward, fuel will run ot of the carb while choking, if the engine will not start You are pulling raw fuel out of the carb float bowl. If the engine starts, raw fuel is drawn in by engine vacuam.

Re: Gas coming out carb during cranking

I agree with MIKESEA. Same thing happened to me a I had a broken REED.

Re: Gas coming out carb during cranking

The engine was tilted slightly forward and fuel would run out of the carb when the engine died. Upon restart it was abnormally difficult to start (heavy choking required).

I do recall placing the clip that connects the needle valve and the float when I rebuilt the carb.

I tested the needle valve by blowing in the fuel line and moving the float and it operated properly. When float was closed it created pressure (full bowl state) in the line and when open it allowed air through (empty bowl state). Additionally, the primer bulb gets extremely hard after 3-5 squeezes.

I have looked around a bit about reeds and and have never heard of them before. Could someone please describe their location and function?

I am going to check the reed(s) tomorrow and soak and clean the carb. Has anyone found those aluminum caps included in the carb kits at the hardware stores; the ones that are flattened with a punch. I would like to remove them for the cleaning, but dont want to buy a carb kit just to get new ones?

Compression: I will see if I can find my compression tester and run a check on it tomorrow as well.
Thanks for everyones' input