76 40hp evinrude carb question

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hardwater fisherman

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Model 40604R. When the fuel bowl is drained or run dry of fuel the bulb will not fill the fuel bowl. I need to spray a little mixed fuel in the carb throat and it starts right up, and fills the the fuel bowl instantly. It remains full until I either drain it or run it dry again. I have tried two different tanks and fuel lines with the same results. Both tanks and lines fill the fuel bowl on my 4hp. So I dont think there is a problem with the fuel supply. What are some of the causes for this?
 
gm280

gm280

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When you squeeze the primer bulb, it should push through the fuel pump to the carb. So either you are not priming enough, or you have a problem with the fuel pump... Fuel pumps have one way valves in them to channel the fuel only towards the carb and not back to the tank. Check it out and see. JMHO!
 
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F_R

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Dumb question from me: You ARE squeezing the primer bulb to fill it and not relying on the fuel pump to do it, right? Can we assume that by fuel bowl, you mean the carburetor float bowl and you don't have something else added there? I am thinking the float valve is sticking shut and the vibration after you start it is shaking it open. But if you run it dry, the valve should already be open. I dunno. If it is sticking shut, the clip may be missing on the float valve needle. Drain the carburetor, then with the drain plug still out, squeeze the primer bulb. Does gas appear?​
 
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hardwater fisherman

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Yes by fuel bowl I mean carb float bowl. Before on a cold start if I pumped the bulb too much fuel would overflow the bowl and come out the throat of the carb. The last two times I needed to prime it ,as said before. This afternoon after work I will drain it and pump the bulb with the drain screw out. No work has been done on the carb by me other than a cleaning .And I did replace the slow speed needle a few years ago. I will do the test and get back to you later.
 
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F_R

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Actually, fuel should not overflow out the carb throat unless the float valve is not doing it's job, or you are really mashing hard on the primer bulb.
 
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Sunken Ship

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If fuel is running out of the carb then the float valve is not shutting the fuel off. I just went through this on my '75 40hp. That is the last of the last to shut fuel down in the process of fuel delivery-aside from actual suction/siphon while the engine is running. There is a video of a guy restoring a '75 40hp Evinrude on youtube that I suspect people are watching-extremely helpful. Although, the guy wrongly puts the float valve hook through the hole on the float arm, which causes binding thus preventing the needle valve from closing.

If we look at GM280's carb pictures in his restore thread we can seen that the hook does not go through that hole. Since doing mine to match GM280's picture I have not had any problems with this.

Just another thing to consider. Gm280's restore thread is awesome! Take a few minutes if you can to review. We get to see our engines completely torn down and gain a lot of knowledge from his work.
 
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hardwater fisherman

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Update.. The float bowl was empty because the last time I ran it dry. So I pumped the bulb until it was hard and it started right up. Then after shutdown I drained the bowl. I pumped the bulb and there was fuel coming through to the carb. I will be going fishing weekly or at least 3 times a month until freeze up so I will not run it dry until storage time. I have a carb kit with float that I bought last year, but it has been running the best since I have owned it.So I did not want to mess with it.
 
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hardwater fisherman

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Went out this morning on the lake and it would not start until I shot a tiny bit of fuel in the throat of the carb. The float bowl was left full from 3 days ago. So I would assume that it is time to open up the carb and clean it and install the kit I have. It is a shame because other than not cold starting sometimes, it is okay.
 
gm280

gm280

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hardwater fisherman said:
Went out this morning on the lake and it would not start until I shot a tiny bit of fuel in the throat of the carb. The float bowl was left full from 3 days ago. So I would assume that it is time to open up the carb and clean it and install the kit I have. It is a shame because other than not cold starting sometimes, it is okay.
Click to expand...

hardwater, rebuilding the carb is a good idea. But it sounds like you are having a choke issue as well. The only time a choke is needed is when the engine is cold and starting it for the first time. But that would be more of the reason you are spraying fuel into the carb throat to get it started then a dirtied up carb. Clean and install the carb kit. That never hurts, but check to see why you can't push the ignition key switch and close the choke system as well. That will allow you to crank without spraying extra fuel into the carb to start a cold engine. JMHO!
 
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hardwater fisherman

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I think i fixed the problem and thanks to everyone who made responses. When gm280 mentioned a choke issue I went out and took a look. The spring that closes and holds the plate closed was out of its seat. Makes me feel kind of stupid that I did not see that before. It started well in driveway as always so I will see for sure next weekend if that was the problem.
 
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