1986-1988 Evinrude 40 hp Idle

Rwilmarth

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Cant really make out the serial number its either an E40RCCS, or E40RCDS. 2 cycle 2 cyl, has both electric and rope start. either way there is minimal difference between the two.

​My question/Concern/problem is that I cannot get the motor to idle at all with the butterfly completely closed using muffs.. it will start and run for 3 seconds or so sometimes less. It will idle beautifully if I set the cam/roller to just apply slight pressure, so if its cracked at all its still 99% Closed. there is no issue with starting, starts instantly every time.

The manual and the sync and link procedure want to have the valve completely closed, and eludes to the cam not touching the roller at all at idle, but does say some models the idle adjustment screw needs to have the cam touching the roller, and to reset the Idle screw after that portion of the sync has been completed.
the manual continually refers to multiple 40hp models with slightly different internal mechanisms to control the throttle

i had assumed that I had gunk in the carbs that had gummed up the low speed circuit, so i thoroughly cleaned and rebuilt the carbs, and changed the internal fuel lines just for good measure. i did visually inspect the reeds, several times, all looked good there, all closed and clean. put it all back together, synced and linked.

timing is as follows idling around -2 tdc, throttle just cracked advances to 4TDC, max advance is 20TDC, using joe reeves method.

I'm wondering if I have a problem as it runs great otherwise.

I do seem to only get about 75% WOT response though. it seems to be getting good RPM's ( have yet to guage it) above 4000 for sure. theres just 1/4 throttle left where there is just no additional response, it doesn't bog, quit, stutter or skip, the last 1/4 throttle opening is just level. pushes my 13 ' whaler at about 30mph via GPS. max rpm is 5500

This is before i rebuilt the carbs so i'm interested to see if that has changed since the carb clean and link and synch. it also smoked a bit more than i would say is normal, which i attributed to the carbs being dirty and a strong gas mix. also i'm not sure if the two things are related, i just assumed the were

new plugs gapped at .40, Carbs rebuilt, sync and link, reset the timing, cleaned fuel filter/pump, compression is 115/112, nice snappy spark jumping 1/2 inch

all seems well, I'm just not sure if there is a problem that's being masked by having the carb open a touch at idle. i would like to have it operating at 100% and not cover up issues.

my model does have the infamous red lever for the primer, auto. (truth be told I've not messed with it under normal operation only to rope start once). I do not know if it has quick start or not, even though it does rev to about 1200 then die back to 900 or so. I attribute the quick start i experience to the primer system. and that little extra squirt of fuel with minimal air.

my thought process tells me that the throttle plate needs to have pressure because all other settings are correct?
 

oldboat1

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lot's there. The oem plug is a Champion QL77JC4 -- should be gapped at .030 (OMC changed instructions sometime during the '80s, going back to .030). Can't do much in the way of fine tuning on muffs, as back pressure is needed (i.e., a large trash barrel, running at idle or high idle). Gas mix is 50:1 if mixing yourself. The red primer lever should be parallel with the primer body for running.

Prop in good shape?
 

Rwilmarth

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I regapped the plugs, and it seemed to run a little better. Regardless of the plug gap, it will not idle, without slight pressure on the throttle roller. Is that nornal?
 

oldboat1

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Roller should just kiss the cam at the mark when throttling up -- throttle plate should start to open at that point. With further throttle up, the cam roller is pushed back to the point where the plate is fully open. Prior to touching the mark, the roller is not in contact with the cam.

Compression might be on the low side. Spark you describe is good.

Not sure what is meant by a "strong gas mix"

Sounds, though, like your top end is good.
 

Rwilmarth

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If I don't have a slight bit of positive pressure from the the cam to the roller the motor won't idle, the throttle is still closed/ cracked open ever so slightly.

I feel like the manual wants me to have it idle without that touching, with timing advance building the revs until the roller touches the cam at the top mark
 

Rwilmarth

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I'm at a loss for what the problem could be if any? Primer solonoid, or lines from that, there is 0 change in idle from auto to manual. I leave it in auto?
 

oldboat1

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The motor will and should idle without the roller touching the cam. It is synced to the timing plate by setting the roller as described above -- throttle plate opens while the timing is advanced. There will also be a throttle idle stop that allows you to manually keep the throttle at a higher setting.

I'm not sure what operation problem you are trying to address -- top end rpms? boat speed?

Don't rev the engine by manually opening the throttle with the roller without advancing the timing plate -- potential runaway engine.
 

Rwilmarth

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Had it in the water today, nice low idol, fresh link and synch got rid of the unresponsive top end. Plenty of get up and go. All great. Engine runs like a champ.

But the roller is ever so slightly cracking the the butterfly open a c hair. I don't think it's normal, but I can't find anything wrong. I guess I'm looking for suggestions???
 

juno pierrat

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Id try turning idle adjust screw in half a turn. Any difference ? Then another half turn. Keep track of turns. If no improvement go back to starting point
 

Rwilmarth

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I could turn the idle screw in completely and it still would not idle unless the throttle was cracked
 

juno pierrat

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did you remove core plugs during cleaning and rebuild? my 48SPL idles around 800-900 in water and 12- 13 hundred on the muffs.
 

Rwilmarth

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Idles at 6-700 in gear, could probably get it down around 500 if I tried. In the water in gear., about 1000 on the muffs.
Did not take out the cores, or welch's.

Did soak the carbs over night in carb cleaner, then spent about an hour per carb running wires and brushes through the different orifices, then further cleared them out using carb cleaner, finally blew compressed air back through, and reassembled using all new components, made sure the floats Sat correctly, gave them the blow test and reassembled
 

oldboat1

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linkage issue maybe -- throttle return spring? You know the plate is slightly open because you reach in and feel it? maybe see it cracked open by looking in through the throat? Maybe the engine throttle linkage needs adjustment(?)
 

Rwilmarth

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Linkage seems good, I have full range? Springs are snappy, I'm wondering if it's the way it should be? Do all two strokes idle with no pressure on the throttle plate?
 

juno pierrat

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there are, I think, two very small holes under the welch / core plug on each carb, replacements plugs come in rebuild kits. those holes are part of the idle circuit, you may have ran wires thru them, they are after the throttle plates and can be cleaned without removing plug or just remove plugs and wire clean them that way.
and for me , mine idles with out roller touching the throttle cam. ie: no pressure on throttle plate
 

Rwilmarth

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Yes, I almost missed those, as they are nearly invisible. I verified carb cleaner would spray through those orifices before I assembled.
 

oldboat1

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http://www.leeroysramblings.com/Johnson 9.9_15.htm (pic of throttle plates, about the middle of the page)

assumptions.... One of mine is that the holes in the throttle plate allow fuel to pass with the plates closed -- that is, the motor can idle without the throttle plate being opened(?) With that in mind, the throttle plate should be closed (I assume) until it begins to open by contact with the cam follower roller.
 

Rwilmarth

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I thought the holes in the throttle plate we're to let the right amount of air through, to suck in the right amount of fuel for the venturi. Those holes are clear, as are the two tiny holes after the valve for the fuel idle circuit. I wish I knew why it won't idle withoutpressure being applied to the roller.
 

oldboat1

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draws air and fuel at idle under high vacuum. I would pull off the carb and examine the throttle plate and linkage. Plate may be constructed with a small opening around the edge to allow air/fuel passage when the plate is closed -- which it should be at low idle, I believe. Idle orifice must be perfectly clean, along with the passages at the top of the carb, and you may need to adjust the throttle stop to permit low idle without stalling.
 
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