Evinrude 90/140 Set Timing at Idle

[JasinC19]

Hey guys, I've been working on getting this motor running well.

I have a rebuilt '79 140 powerhead with all the ignition (and now intake manifold) from a '97 v4 90. Both are 90 degree crossflow motors.

I am using the carbs from the '79 140hp and the air box from the '97 90hp. Would this be an issue?

I am going through the procedure to get the motor to idle.

The engine basically idles poorly unless I advance the timing at idle to be closer to 10 degrees. At that point I can raise the rpms using idle adjust screw to be around 1000rpm. It's only on the hose so I assume the idle will drop in the water.


From what I understand, the correct procedure is to disconnect the teleflex cable from the throttle lever. Ensure that the throttle cam is adjusted back so as the butterflies on carbs are closed.

At that point start motor, get her warmed up and set timing to 5 degrees atdc. Then adjust teleflex and throttle cam so that they are locked in at that exact spot.

Then use the throttle adjust screw to work the whole assembly at once to raise idle (and spark advance) at once.

But the idle is extremely muddy when I do this. When I advance the timing to be closer to 10 degrees atdc, idle cleans up and motor seems happy...

Can you give me any pointers?

 

[Bosunsmate]

Maybe im wrong but going from 5 to 10degs atdc sounds like you are retarding the timing.
Have you marked all the cylinders and checked they are firing approximately in correct time?
Maybe one is out of whack.
Also check joe reeves method for checking timing. its in the stickys at the top of the threads

 

[flyingscott]

Do you have the factory manual for the motor that you used the linkages off of. Idle timing is a very misunderstood thing. The idle timing is where the carbs just start to open. It does not need to idle there,

 

[JasinC19]

I'm retarding something, just not my timing

I meant btdc. I found the sticky you referred to. Thanks!

I'm not sure how to check firing order. I did confirm via wiring diagram that my cdi wires were hooked up to the correct cylinders.

 

[JasinC19]

flyingscott - since the time of posting I have both seloc manuals for the '79 and the '97. It is saying to set the max rpm timing first. I am going to try to do that in the next couple of days.

As for the idle speed/timing - it is confusing because once I set max rpm timing, any changes to idle timing will throw off max rpm timing. The reason for this is because the '97 linkages do not include a maximum spark advance stopper. The throttle cam is set up so that after a certain point of acceleration, it will not advance the spark advance arm anymore.

The '79 linkage system does include an adjustable maximum spark advance stopper. I can provide pictures if needs be.

So I am hoping that the timing will be correct at idle after I set it to 28 btdc at 5000rpm.

As for idle rpm, am I correct in saying that if I turn the idle screw in, the whole linkage system opens and the butterflies on the carbs may be cracked open, even in neutral?

The manuals/procedures state that the carbs need to be closed while setting idle timing. But raising rpm's using idle screw will need to open carbs in order to work right? The only other way would be to adjust the throttle cam to keep the butterflies closed as I adjust the idle speed screw, which would just advance spark timing at idle.

Just trying to understand the whole concept.

 

[Bosunsmate]

To need that much advancement of timing at idle seems out of whack.
Normally its atdc at idle and comes through tdc to btdc as you accelerate away.
Is your flywheel key ok?
Hows compression?