1964 40HP Evinrude Big Twin - Always have to ch.hoke to start

[newhamburgboating]

Hey Folks,

My motor always needs to be choked to start. I ran WOT for 20 minutes to make sure it was full temp. Shut it off, chug chug chug chug. close the throttle and vroom! then open the choke back to auto and off we go.

I should mention i get healthy RPM (4800) at WOT, I can Idle at 3km/h (walking speed for the americans) @ 700rpm smooth.

It wouldn't be such a big deal normally but my automatic choke has ceased to work and its a pain in the ass with just me or someone afraid of the motor with me in the back.

Thanks in advance for any feedback!
Steve

 

[gm280]

Maybe you have a little weak compression and therefore it doesn't have enough draw to pull enough fuel through the normal carb setup to fire it up. And the choke offers that little extra to get it running. So It looks like you need to repair the non-functioning choke now... JMHO!

 

[newhamburgboating]

Thanks gm280,

Last year i checked compression and had high 90's on both. they were within 2PSI. I hope nothing like that changed over the winter in my garage.

Do you know much about those auto chokes? Is seems to have some dangling weight that sits into a cylinder where the voltage connects. almost like a film canister.

 

[racerone]

Have you tried adjusting the choke spring tension or is the electric overide not working ?-----Lot of used parts available for that motor in southern Ontario.

 

[newhamburgboating]

Hey racerone,

How could I adjust the tension on the choke spring? And I should be able to see 12v on that wire when pressing the choke right? is that the override you are talking about?

I don't see the butterfly in the carb move when on the auto setting and choking it remotely.

i think gm280 is right, likely easier to fix the choke then troubleshoot a no choke starting issue.

 

[racerone]

3 screws and you can inspect the internal bits of the choke.---Post pictures of what you see when cover is off.

 

[newhamburgboating]

Well I took the round plate off the side of the choke. The cylinder that drops down into the canister was stuck midway. I simply pushed it down and now it bounces freely. Hitting the choke makes a loud click and slams the butterfly closed.

How much tension should be on the wound spring? I did a mark where it was sitting before i took it off but would much rather set the tension myself according to guidelines.

 

[racerone]

The canister is the solenoid that pulls the choke on with the switch.---Rather than explain how to set the choke your best bet is to set it where it was and adjust till you get the desired results.--Trial and error method.---I have lots of parts available for those motors and travel through the southern Ontario area.

 

[newhamburgboating]

Ok, so just to start off then. the butterfly has a tiny bit of pressure applied from the coiled spring. this has the choke alomst closed. i would say 80-90%. when i engage the electric choke it slams it the rest of the way closed.

So my understanding is that when the motor is running it wants to suck in air. therefore the butterfly will open up from the incoming air pressure.

then, when the motor is warm the exhaust heat heats the coiled spring which in turn takes all the pressure off the butterfly and lets it open easier.

Correct?

I mean i can spin the round plate once and it puts a fair amount of pressure on the butterfly. seems too stiff imo

Thanks again! almost there

 

[F_R]

Your description sounds reasonable. Is the heat tube functional and the "stove" inside the exhaust not corroded through? Is the open end of the heat exchanger not plugged? Some people see that open hole and just can't stand it so they plug it---then wonder why it doesn't work. If your motor truly is a 1964, then the choke switch has been changed from an "over-ride" to a "choke" switch. That is good, just don't get confused when people talk about an over ride.

To verify, the bi-metal spring partially chokes it until warmed up, then the choke should be open. The electric solenoid slams it tight shut for a cold start. You shouldn't have to be opening the door to do it at the motor. Be sure you leave the manual lever in "automatic" so it can function.

 

[newhamburgboating]

Hey F_R, seems you always find my \posts, thanks for helping!

I'm not sure what to look when you ask about "stove" being functional. I believe it to work because that tube that runs from the back of the motor to the bi-metal spring choke becomes hotter then just touching the engine block after warm up. being hotter and external to the motor one would have to assume it's doing it's job right?

so on a resting cold motor the choke butterfly should be close to closed. and after the motor is warmed up, wide open?