Fisherman's Poor Idle -

[notop]

I have a '67 Evinrude 6hp (Fisherman) that doesn't want to idle properly.
Starts up very well, 1st or 2nd pull. But if I ease the throttle down from the start position, as soon as the roller on the throttle gets off the timing cam, the engine wants to die. The only way I can keep it running is to pull the choke handle out about 3/8"or so, until the choke lever just touches the throttle lever and nudges the throttle. Once I do this, I can idle down quite a ways and set my slow idle needle. But if I take the choke off, she dies.
My service manual does not show any adjustments for the carb other than making sure that the float is level with the rim, and the slow idle needle adjustment. Is there any kind of adjustment for the choke or throttle-butterfly valve to set it properly? The carb was a bit gunked up last year, but I had it cleaned at a marine shop and a few days ago I took the bowl off myself and everything looks clean and the main jet is does not appear to be blocked or damaged as far as I can tell.
Not sure if this has anything to do with the idle, but compression is only about 77 and 78 lbs on this engine -- can that cause this type of bad idling performance?

 

[JohnRudeMan]

Re: Fisherman's Poor Idle -

The low compression could be the problem for the poor idle on your motor. The compression on that six hp should be higher.

Greetings

 

[kbait]

Re: Fisherman's Poor Idle -

Something's up w/fuel delivery if you can choke it to get it to idle lower. Compression is likely fine, as you can't spin those motors very fast w/recoil. First, confirm 1/4" bright blue bolt on each plug lead with a tester as weak spark can mimic carb issues. If that's good, confirm link/sync.. search this forum for details. If that's all correct, disassemble carb and clean again - paying particular attention to low speed circuit. Replace low speed needle packing and fuel line (5/32") from pump to carb and try again.

 

[OptsyEagle]

Re: Fisherman's Poor Idle -

But if I ease the throttle down from the start position, as soon as the roller on the throttle gets off the timing cam, the engine wants to die.

I do not have a 67 6 Hp but I do have a 1961 5.5Hp which I believe was the start of the 6Hp design. In any event, my motor does not have a kill switch so all I do is turn the throttle off and it stops. I assume you can't turn a throttle more off then when the rollers gets off the timing cam, so all I can say is that your condition sounds normal to me.

Maybe you or someone else can see what I am missing.

 

[kbait]

Re: Fisherman's Poor Idle -

Hey Optsy, If the link/sync is set correctly, when the cam roller hits the cam, it's at a medium/low idle. You can usually slow it more w/just the mag plate moving (timing), even if the roller isn't touching anymore. When it's all good, you should be able to go VERY slow and steady..

 

[HighTrim]

Re: Fisherman's Poor Idle -

I agree with Kbait, I dont think the compression is too low for that motor, especially pulling manually to test.

If the ignition system is producing a hot bright blue spark that jumps the 1/4" gap every time with a nice SNAP!! then the low speed circuit is to blame. How did you set your needle? What is its condition, taper smooth and tip not broken? Proper packing, no air leaks?

I realize I just suggested much of what Kbait did, but agree with him.

I have a couple small hp motors that will idle right down on no throttle with a steady Thump..........Thump.......Thump........

 

[notop]

Re: Fisherman's Poor Idle -

Spark : It does travel 1/4". It is blue, even in daylight. It jolts like hell when you put yourself in it's path. Don't ask how I know the last part.
Fuel pump: Disaassembled -- membranes all look fine, filter screen is very clean.
Fuel lines: Removed and then I huffed and I puffed. Now I have the yummy taste of 50:1 in my mouth, but I can at least confirm that the hoses appear to be clear.
Slow idle needle valve: see photo attached. You can see an area there where the needle is somewhat shinier than the rest. I assume that is where it is seating. I cannot *feel* any wear in that spot, but then again, I've hit my fingers with so many hammers over the years its a wonder I can feel anything with them. How does this needle look to you guys?
Additional on needle: packing was all disintegrated between the nut and the body of the carb where the needle valve goes in. Fashioned a new one by boring out a thin slice of 3/16"fuel line and using that as new packing. I am reasonably confident that there is no air leaking through this improvised packing once the nut is done up.
Other photos: Gap between choke lever and throttle linkage with choke completely off. Next shot: with choke pulled out about 5/16" or so and motor idles fine at this point. Should I be trying to bend the tab in the last photo so that this position is maintained when choke is completely in (ie, off)?