84 evinrude140 miss/ cough

[ebear]

I've been at this for days. I'm at the end of my rope. The carbs have been cleaned twice, floats set with factory gauge, plugs and wires replaced, timed to 4 deg,
7/16 spark on all 4, new fuel 40:1, fuel pressure 3ish lbs at idle and the reeds are good. I cannot get rid of this damn cough. when it first starts it'll kill it. After a few minutes of running it will smooth out but still occasionally die. If I push the key it'll change the idle but not necessarily improve it. the plugs are all a little wet when checked. Thanks for any input on this.
I took a video of it yesterday in hopes that it may help.

https://www.youtube.com/watch?v=8WuL2SUoFkU&list=UUNwq3QQOLvXY7_9O8N7eQ-Q

 

[Bob_VT]

I have basically the same motor (mine is an 83). I think most of what I am seeing /hearing in the video is normal however, mine is EXTREMELY picky baout the carbs being perfect. I suspect that some of the passages might be blocked and I would double check the float adjustments. When I do my carbs it takes me a few hours and when I assemble them it is done on a clean white towel. I am very meticulous with the carbs....... but t hat is me.

 

[racerone]

Compression test results ?

 

[ebear]

Compression is 100-112.
It may be nothing but I did notice that the idle / timing screw, in order to get 4 degrees. it needed to be turned in to about 3/8 inch from the head of the screw. It looks like it's way further then where it should be.

 

[Tim Frank]

Doesn't seem much wrong there.... so you may be looking for small issues.
What plug are you using, and 40:1 is a bit lean....not much, agreed,

Also, you have not given any history....that usually is really helpful.
Is this motor new to you? (there may be all sorts of "previous-ownerisms" that you acquired.
If so, has it ever run to your satisfaction?

 

[metriccrescentwrench]

I recently purchased an '84 'Rude 140 for my latest project boat...... Did you follow the procedure for a 'link and synch' from the factory manual? All carbs need to be totally closed at idle, they all need to begin opening at the same time, and the throttle should advance timing to 5 degrees BTDC before the timing cam starts to open the carbs (and should be at the mark on the timing cam when this happens). If all of that isn't perfect this engine will idle like crap.

Also, if all of that is correct don't fret about the idle timing too much, just set it to wherever it needs to be to idle around 650 rpm in gear and floating free. FYI my idle adjustment screw has to be most of the way in to get it correct.

And as far as compression, for one point of comparison mine is at 120 - 125 on all 4.

 

[ebear]

history that I know:
the guy I got it from said that someone reversed polarity on the battery. It murdered the rectifier. replaced that and spark came back. Spent today going all over the carbs. Messed with the floats, cleaned and cleaned and cleaned again. It acts like a lean condition but It will not change even if I change the float height. There is no consistency to what its doing. I'm to the point now that I'm thinking intermittent failure of the trigger. It meters correctly but I'm running out of options. As far as linkage n stuff. Absolutely by the book. Tried timing from 2 all the way to 6 degrees no change and I cannot get it to idle lower than 900 without it dying
signed: about to blow the effer up

 

[racerone]

Verify that maximum timing advance is still correct.------Idle timing is where the throttle plates open up and thus that is a linkage / carburetor adjustment.

 

[Tim Frank]

I usually give the manufacturer the benefit of the doubt that they put the right parts in at the factory.....but that doesn't extend to previous owners....do you even know how many owners the engine has had?
I'd verify all the jets in those carbs as a starting point. There are a lot of different configs that were used from the same base unit for different models and HP.

 

[rothfm]

TIm Frank brings up a good point, and worth checking....I have had mix/match jets in carbs that threw me off terribly. And different even between each carb! Ya never know.

Also ensure all fuel lines have very good tight clamps on them.

 

[Bosunsmate]

Plugs are a bit wet...
Id try mixing 50/1,
Hows the temp?

 

[Bosunsmate]

Also have you checked tdc lines up with tdc on the flywheel mark?

 

[emdsapmgr]

I don't hear a lot of lean sneezing. The engine seems to labor when trying to start. The timing may be off. If you are trying to get it to idle at 900 on the trailer, you are setting the idle incorrectly and that may be the problem. The idle must be set when the boat is floating normally in the lake and it's shifted into forward gear. Set the idle by the tach so it's at 650-700 rpm's-in gear. You can't set it on the trailer. Do not worry about the idle timing degrees, they will be different for every engine and depends on how deep the boat sits in the water. The resulting prop backpressure will make the idle adjustment unique to just your boat. Set it for the idle rpm's and the idle timing degrees won't matter. What you will find is that once you set the idle correctly, the engine will idle at maybe 1100-1200 rpm's when on the trailer when running on the garden hose. That's normal.

 

[metriccrescentwrench]

.....What you will find is that once you set the idle correctly, the engine will idle at maybe 1100-1200 rpm's when on the trailer when running on the garden hose. That's normal.

That's right on the money for both of my current engines ('96 Rude 175 and '84 Rude 140). In fact I've figured out that if I set them to around 1100 rpm on the trailer (before I was able to lake test them) that they're pretty darned close to where they need to be.

 

[ebear]

Problem solved. Apparently,off idle there is enough energy coming from the trigger to run smoothly. at idle no, unless I smashed ( not squeezed) the connector to the power pack together. removed the connector hard wired it and now it idles good. Barely bad connector? In a perfect world even connectors will be go/ no go. thank you guys for all the input.