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1985 Evinrude 50 HP E50BELCO wont idle without engaging primer

Progator135

Progator135

Regular Contributor
This is whoopin me..good compression and spark...carbs gone through...clean as a whistle..fuel pump freshly rebuilt (VRO Removed and regular pump put on the pulse hole on side..Front pulse hole has plug)..no change...All fuel lines in good shape and not sucking air. runs great when you advance it to a fast idle..but when brought back to shift gears, will slowly starve and die unless you shoot some gas to it with the key..then itll recover. Ive advanced the idle screw almost all the way no help.
My theory: tell me if im on track...theres a fair amount of slop in the butterfly shaft going thru the carb -both of em...getting more air than in needs from the wallered out shaft holes..but not gettin the gas because theres no suction at the gas tube because its in front of the butterfly....shoot gas from the primer and it goes in behind the butterfly and gets the air/fuel ratio where it needs to be. ( it will die out if you hold it too long. - just a quick tap in on the key is all it takes to keep it alive)
Once you start advancing it accellerates smoothly and runs like a top. Just dying at idle...makes trailering fun.:rolleyes:
How about float level adjustment? They were set barely off level..(looking upside down the non-hinged side was a tad higher) Thats right aint it?
What about bigger Idle jets?
 
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I've had an idle problem before, mine was fixed when the charge coil under flywheel finally failed completely. testing stuff under the flywheel takes a special volt meter and there are many posts on here that explain how its done. But for me with no special tools i took flywheel off and found a dark brown goo draining from charge coil. a sure sign it was bad, have you had flywheel off lately
also i removed fuel connector at engine cowling and ran straight to pump.
do you have an inline fuel filter? changed lately?
 
In engaging the fuel primer solenoid to keep the engine running, you are simply bypassing both carburetors and applying the fuel mixture directly to the intake manifold. This proves that your problem is "fuel" related.

NOTE: The idle jets meter "air" not fuel. To richen the idle fuel flow, one must decrease the ID size of the jet! I suggest you leave those alone for the time being.

If pumping the fuel primer bulb constantly (acting as a manual fuel pump) cures the idle problem, then obviously you have a faulty fuel pump... or a fuel/air leak at some point between the fuel pump and the fuel supply. If this makes no difference, read on.

If the throttle shafts are worn... OR... the holes in the carburetors are worn, in either case that will obviously allow excess air to conflict with the jet settings. However, it's best not to assume this is the problem but to look closely at the fuel passageways of the carburetors once more as something may have been overlooked (it happens).

Mainly... the small brass tube you see attached to the upper body of the carburetor that leads from the extreme bottom of the center casting to the upper portion of the carburetor... that is the idle fuel passageway which is easily clogged/restricted. Make absolutely sure that it is perfectly clear... clean it thoroughly with a thin piece of single strand steel wire and compressed air.

Let us know what you find.
 
Hmmm..well I had the carbs apart...pulled all the orifices...shot carb cleaner thru all the passages, everything appeared free and clean. I'll reattack and make sure. Squeezing the primer makes no difference at all. If I'm standing next to it on the hose the only thing that brings it back to life for a few seconds is opening the carbs a tiny bit manually or momentarily turning the red lever on the primer to 9:00 then back to 3 real quick.
 
Turning the red lever puts the primer in the open position.-----Fuel is then sprayed into the carburetors by the fuel pump.-----------This fuel bypasses all passage ways in the carburetors.--------This points at problems with carburation.------Did you remove the high speed jet found horizontally in the carburetor bowl ?
 
Had the same problem with a 88 70hp 3 cylinder. Ran great, until it would stop again. Had rebuilt the carbs. Fuel lines were degrading and getting rubber into the carbs. They are past the filter so it does no good to think the filter will keep it out.

That was my problem. All new lines and problem fixed. (after I cleaned the carbs out yet again)
 
New fuel lines are sitting on the workbench...the old ones appear to be in good shape but that's just from an initial inspection. They'll be changed when I go after the carbs again. Racerone...yes I unscrewed and inspected both orifices on my initial inspection. Couldn't look any newer.
 
Nope...didn't put new gaskets and tightened the crap out of em. Not to the point of snapping studs off but theyre tight. Didnt even consider the mount surface leaking but I'll add that to my list. Never had that happen at the mount surface..always hear about it...but never had it happen...but that is sound advice i will definitely be taking a close look at. I have a sheet of gasket material ..I'll make some new ones up and rule that out! I appreciate all the help!
Edit: the other question about choking the carbs by hand: it crossed my mind to try it...I gave it a half a**ed attempt but i had the inner cover plate still attached and couldnt really get a good seal on both carbs at the same time. If all the above doesn't fix it then I'll get a rag and fold it over a few times and use that.
 
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Update: pulled carbs and went back thru them - every passage checked with wire and blew out with air. Everything clean as a pin. mounting surface was clean and the existing gaskets are in great shape - no way air is getting in there. Float valves clean and functioning as advertised. Fuel lines replaced - the " tree" where all the fuel lines hook up after VRO removal was inspected/cleaned. saw some deterioration inside the fluel lines and got all excited. but that proved not to be the cause. Reed valves also thoroughly inspected and all is well. PUt everything back together...same thing. Needs extra boost of gas to stay running. at idle. Its GOT to be the butterfly shafts. They have over 1/16" of slop in both sides of both carbs. No way theyre not sucking massive amounts of air. I appreciate all the ideas - gave me the initiative to give everything one more good look before I order new carbs. UNless somebody has an ingenuis fix for it. Has anybody put little tiny O-rings on the shafts to try to seal it? Just a crazy thought...
 
Squirt some thick oil on those throttle shafts when motor is running.----The oil will act as a seal for this test.-------Your results may vary.
 
Go back and re-read Joe Reeves' post.

I will cut some of his words in:

"Mainly... the small brass tube you see attached to the upper body of the carburetor that leads from the extreme bottom of the center casting to the upper portion of the carburetor... that is the idle fuel passageway which is easily clogged/restricted. Make absolutely sure that it is perfectly clear... clean it thoroughly with a thin piece of single strand steel wire and compressed air."

Follow the fuel flow path from the bowl to the venturis. You will see that the fuel goes from the bowl, up that small brass tube Joe is referring to, into a chamber that is under the silver core plug on the top of the carb. In that chamber there are tiny holes that allow fuel to enter the venturi bore directly behind the throttle butterfly. If you have not removed that core plug to clean those holes, it cannot get idle fuel. Have to use a fine wire.
 
daselbee said:
If you have not removed that core plug to clean those holes, it cannot get idle fuel. Have to use a fine wire.
Click to expand...

ooohhh I see....I did NOT pull that plug or see those tiny holes...didnt know thats what he was referring to. I did just as he said... I just ran wire up the little tube and blew air into it...which came out the idle bleed orifice...thank you for clearing that up...maybe theres hope yet. ..well back into em again this evening if im not rained out.....crazy as it sounds, I hope I pull that plug and its jam packed with garbage in there.

Racerone...good Idea..will try that..but I sure hope that I find some plugged holes mentioned above.
 
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Well, popped the plugs and of course...clean as a pin..:mad:..gotta be the shafts...I took the tiniest o-ring i had from my kit, stretched it over the shaft and put it on the spring side, put everything back together and it looks liek it will make a good seal. the spring itself keeps it pushed up against the carb body just enough to block the gap but not hinder shaft rotation. Thats all I got...Im out of options...didnt test it yet...it got too late. I did check the butterflies themselves very closely and they are centered nicely and making a nice seal inside the carb throat. all new lines, every passage and jet and orifice in the carb is like it came off the shelf yesterday...
I did discover however that there was supposed to be a gasket between the air intake cover and the carbs. wasnt one...would that affect the idle? I wouldnt think so but an old post from 2009 by joe reeves says otherwise. Keeping my fingers crossed.
 
The gasket on the air cover is simply to keep the fuel/oil mixture from dripping into the lower engine pan.

A 1/16" vertical play in the throttle butterfly shafts will of course prevent the engine from idling properly.

Pertaining to air being drawn between two metal areas.... that happened back in (I think) 1983 where the intake manifold would not seal properly against the forward portion of the crankcase. OMC's recommendation which cured the problem perfectly was to simply double gasket that area.

Bottom line... don't take a chance of making the metal area worse, just add another gasket.
 
Quote from Joe Reeves 8-21-2002 : ""Scottg.... If by "airbox", you're speaking of the heavy duty carburetor intake face plate assy, the engine will do all sorts of weird things if you attempt to run it without that assy attached. It acts as sort of a air restrictor, and that thick gasket that presses up against the carburetors absolutely must be there."

Bet you didnt think your words of wisdom would be floating around 12 years later did ya?! :p
 
Progator135 said:
Quote from Joe Reeves 8-21-2002 : ""Scottg.... If by "airbox", you're speaking of the heavy duty carburetor intake face plate assy, the engine will do all sorts of weird things if you attempt to run it without that assy attached. It acts as sort of a air restrictor, and that thick gasket that presses up against the carburetors absolutely must be there."

Bet you didnt think your words of wisdom would be floating around 12 years later did ya?! :p
Click to expand...

Actually once they're there on the Internet... they're there forever just about. However, that statement pertains to the "Loop Charged" 120hp, 140hp, and in particular the V6 models... NOT your 50hp model.
 
Ahh I see...well I made a gasket for it anyways....And to update: The tiny o-rings on the shafts definitely made a difference. had it idling pretty good. It's still not perfect but definitely a marked improvement. It idles long enough for me to shift gears now anyways. And just the tiniest amount of restriction by lightly placing a rag over the carbs got it where it needed to be. I lightly shot a little brake cleaner right on the o-rings I installed and you could hear the rpms go up. so its still drawing some air thru there. But its better. The upper carb was mostly the problem, the shaft was extremely worn. even the return spring had worn grooves in it. I have a tournament this saturday I have to make so I patched it all together with the o rings and will have to deal with it till I can find some new butterfly shafts. Appreciate all the advice...
 
:confused:....can anybody help me find a throttle shaft?.....been searching all morning...not on parts breakdown...not on ebay.... like tryin to put socks on a rooster...maybe one of you guys has a couple junked carbs layin around? Name your price...
 
Yeah...looked at that too...I havent even found a source for new carbs. the parts list on here says unavailable for all numbers.
 
Yeah saw those already...also saw lots of others that were cheaper..but a year or 2 off...If I only knew if the shafts were the same in the cheaper ones. I may shoot an offer and see what he says....Thank you all for the help!!!
 
I,ve got a pair of carbs from a J50TLCOB, an 1985 50, there spares if i need them for my 1987 48 SPL. PM me, maybe we can work it out.
 
Man I really appreciate the offer! But I lucked out and swung by a nearby boat repair place this afternoon.. He had a set of older evinrude carbs for something a bit smaller...maybe a 30 or 40 hp. I took em off his hands for $12! They were in a box with about 200 more carbs. He's 75 years old and has been there since I was born - and Im 40! ANyway the shafts were in great shape but needed a little surgery on it to get the 50hp butterfly to fit the flat spot on the shaft. The holes aligned perfect ...about 1/16 on each side with the dremel and done. Threw everything back together and purring like a kitten. I only did the top carb because it was the worst and the linkage mechanism for the bottom was different.
 
HA! Ain't that the truth. And the bores were pretty good. I should take a pic of that shaft I took out..never seen one that bad.
 
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