1979 Evinrude 140943R - wont idle

[daselbee]

Checked idle timing and it only read 2 degrees.

Two degrees WHAT? I just wondered why you left out such a very critical piece of info detail. Reading this post since you started it, and see the resolution....but immediately I had the question....2 degrees WHAT? (If you don't know what the WHAT is....do some more studying.)

 

[scott hamilton]

Two degrees WHAT? I just wondered why you left out such a very critical piece of info detail. Reading this post since you started it, and see the resolution....but immediately I had the question....2 degrees WHAT? (If you don't know what the WHAT is....do some more studying.)

WHAT = btdc, I guess? If not let me know what your talking about. I measured timing and reported at post #6. Before then I had never measured it. I' learning. WrenchHead and Faztbullet nailed it.

 

[daselbee]

Scott.....here is the thing...you have to know whether it was BTDC or ATDC. That motor should idle at or around 4* ATDC. If you have to advance it to 5* BTDC to get it to idle, then something is way wrong. That is a nine degree difference.
That is why I am hung up on this detail. (Details, by the way, make or break a good marine mechanic.)

Uh......you pros out there....I could very well be wrong about the idle timing spec. for that '79 140. This is from memory and some experience. So be sure to correct me if I mis-speak about that 4* idle timing number.

If you were at 2* ATDC and had to go to 5* ATDC....well that's the wrong way....you are retarding the timing and making the problem worse.
If you were at 2* ATDC and had to go to 5* BTDC...well that is seven degrees advanced...and is not right.
If you were at 2*BTDC and went to 5* BTDC...well that is three more degrees advanced, but still way off spec.

See why I want to know the detail?

Last motor I had that would not idle...no matter what I did....I had to set the idle timing to 6* BTDC. It had good compression....110s on all three, spark was in the 7/16 gap jump spec, carbs were spotless.....I checked it all.

What was wrong? The engine was worn out. It was not producing enough crankcase compression to get a good shot of fuel into the cyls.
The bottom of the bores was 0.025 inches oversize, with std pistons in it, and it just couldn't run. It had a real nice ridge at the top of the cylinders, too.
Looked like someone had been puffing BonAmi into the engine thru the carbs....(joke).
Rebuilt the engine...bored 0.030 over, compression still in the 110s, BUT...it idles at 6*ATDC now, where it should be, and starts like a dream.

OK....so if you are at 5*BTDC...possible the engine is seriously worn internally.

 

[daselbee]

Ok, I just looked up the timing...and the WOT timing is to be 28* BTDC.
The other timing spec given is the throttle pickup timing spec.
This is the optimum timing or spec'ed timing for when the timing marks on both the throttle part of the linkage as well as the timing part of the linkage are aligned per the link and sync procedure.
The timing spec is stated at 0-3 degrees BTDC for throttle pickup point.
So that says the timing at idle should be somewhat more advanced than the 0-3 degree BTDC value.

I interpret that to mean that the engine should idle in the TDC to "X" degree ATDC range...with in my example...X being 4*ATDC.

Bottom line...if you are at 5* BTDC for acceptable idle, it could mean the engine is worn.

 

[scott hamilton]

My original 1979 Evinrude service manual for 140943R states set to 4-6 deg btcd idle timing. Mine started at 2 btdc and now reads 5 just as the throttle plates are beginning to open and the roller lined up with the mark on can. Thanks for looking though. I do appreciate it. Hopefully all is well. Sure runs sweet now.

 

[daselbee]

Woah...OK then. I am incorrect. 4-6 BTDC...??? That is surprising to me. Good to go then....