Outboard motor needs choke all the time :-(

[dart]

My outboard runs but needs choke even when hot.

I tried changing the spark plug.

Any ideas what this means?

ta

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[Guest]

Sounds like a blocked fuel jet in the carb. or gummed up.

<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[VicS]

It could be that the mixture adjustment is incorrect, did it run ok? have you altered anything? or that the jet is partially blocked. Is fuel getting through Ok or is the filter in dire need of cleaning. I would check for blockages and clean the float chamber and jet(s) before altering any settings. Have you perhaps used some contaminated fuel. While agreeing that fuel can be kept for long periods in the right conditions it can and does deteriorate if not so stored. I once had some 2stoke oil do something rather nasty after prolonged storage as well.

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[Talbot]

assume you are talking about a little engine . as previously said, could be dirt in the jet. Might be dirty points, points closed, mixture screw been moved etc.

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[Heckler]

here beginneth the lesson, petrol contains light fractions which when vaporised (thats where the american gas comes from) in a carburettor form with air a combustable mixture. when the engine and surrounding temperature is low it is more difficult to vaporise the petrol to form "gas". the choke makes the engine pull more petrol from the main jet thru the emulsion tube and consequently more light fractions that vaporise easily in the low temperature to form a combustible mixture. as the engine temperature rises less light fractions are needed to vaporise to form a perfect combustible mixture and so you can start easing back on the choke.
now, if you have to use the choke all the time it can mean several things are wrong but only one cause, not enough light fractions, the flow of pertrol thru the carb is being obstructed, i.e a globule of water on the main jet, a blocked main jet, verdigris off said water and brass jet blocking main jet, blocked breather on fuel tank OR stale petrol, light ends have evaporated leaving a not easily vaporised liquid that then requires choke to produce enough lighter ends to combust.
all in all anything that stops enough light ends being present to produce a "gas" can cause the problem, spark plugs, points, timing do not come into the equation
stu

<hr width=100% size=1>http://www.beneteau-owners-association.org.uk

 

[longjohnsilver]

Yep almost certainly this, has happened to me several times, easy to unblock with a piece of suitably sized wire.

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[penfold]

Akkkk!
Not a good idea, IMO. If you do that you'll change the size of the hole and knacker the gubbins. Either blow the obstruction out (lungs or compressed air)or disolve it with a tin of aerosol carb cleaner.

cheers,
david

<hr width=100% size=1>It's a mother beautiful bridge, and it's gonna be there!

 

[longjohnsilver]

Well if it's gunged up all the compressed air in the world won't blow it out (I've tried with 3000psi and it doesn't work!!) so wire seems the best option, but must not be over size.

Haven't come across aerosol carb cleaner, what's it called? Certainly sounds the best option.

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[oldharry]

The carb has to mix the right amount of petrol with the right amount of air in order to work efficiently. When the engine is cold it needs rather more petrol, so the choke closes down the air inlet by a precise amount to compensate and enrich the mixture.

If the jets which squirt the petrol into the air intake are blocked by gunge, water dirt etc, then the petrol/air mix is too weak to burn properly. If some petrol is getting through, then closing the choke may bring things back into balance sufficiently to run the engine - sort of!

Bad electrics - whether plug, condensor, points, or electronics are faulty will stop the engine dead in its tracks, or cause it to fail to fire properly on every ignition stroke, causing a staccato and jerky misfire which will not be rectified by playing with the choke. Either the spark is strong enough to ignite the petrol air mix, or it is not with the result that the engine dies not fire on that stroke. The next stroke in a marginal spark situation may be just strong enough to do its job so it kicks the engine over for a few strokes before it fails to fire again - producing the familiar irregular stop start running that we all dread.

Carb Cleaner is marketed as 'Carburettor cleaner' (Wow!), and is quite effective at removing deposits of gum and gunge. However it does not remove solid particles of dirt, nor will it deal with a seriously gunged up carb. Stubborn cases may need to be soaked overnight - which is difficult as it evaporates quite quickly, so everything has to be enclosed. It does not seem to be stocked by every car shop, so you may have to shop around a bit.

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[andyball]

various brands of "carb cleaner" about, but they won't usually touch the gum or varnish that can block jets/make the hole smaller.

A few yrs ago we had an old o/b that someone had let a whole tank/carb' full off petrol evaporate....carb' cleaner didn't touch it, but iso-propyl alcohol certainly did the job, but it probably makes rubber swell up after a bit, so careful if you use it.

regarding poking out jets with wires, done it 100's of times, admittedly with copper or brass wire.

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[ex-Gladys]

The wire approach is fine for older stuff like Seagulls, but do it at your peril on Jap carbs. Manufacturing tolerances and jets are so exact that even if you use brass or copper wire and it's on the piss, you'll per chance ream out the jet, because although their manuf tolerances are fine their metallurgy stinks. Years of Jap motorcycle experience tells me this

There are two types of carb cleaner, aerosol and straight liquid. Agree re aerosol, but a soak in liquid will work. Also you can get carbs cleaned ultrasonically. Very successful, so I understand.

<hr width=100% size=1>Larry Botheras

Anderson 26 "Amber"

 

[andyball]

all the times I did it was on japanese m/c carb's- as I said, no problems...I used to unstrand electrical cable & use it like a small drill, going up a size or two as needed- worked even on very deep small bore pilot jets blocked solid with gunge that nothing sold as carb' cleaner would touch....with pilot jets costing sometimes £12 each & four carb's most customers thought it worth my trying.

Naturally if you take a big old wire & force it through at an angle you'll risk damaging the jet.

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[dart]

Gosh, thanks, plenty to go on here.

I guess I'll have to take it all to bits. Will have to wait for a marina berth and pontoon.

Its a Yamaha 2 BTW and fuel is not stale.

Cheers.

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[Bilgediver]

Hi There

This is mprobably an air leak where the carb attaches to the engine..slacken of the clamp screw and push the carb hard up against the engine or air leakes in where the carb is split to allow for clamping..It must be pushed hard up..this stops arir leaking in then tighten the clamp screw

John

<hr width=100% size=1>Chaka of Birdham MFAX

 

[penfold]

Other thoughts on the gumming problem. In the past I have successfully used paint stripper of various brands to clean out otherwise iredeemably gummed up carbs. dunk the offending piece of carb in a jar of stripper and poke it into the wee holes with a cocktail stick; leave it for a few hours, then pull it out, wash it with fairy liquid and rinse under the hot tap. Hey Presto! one clean piece of monkey metal!

Be careful folks, 'cos paint stripper is nasty.

cheers,
david

<hr width=100% size=1>It's a mother beautiful bridge, and it's gonna be there!

 

[Athene V30]

Before you get to dismantle the engine you haven't done what I did a couple of seasons ago and bought cheap 2 stroke oil? Engine kept stalling / needed choke all the time etc - Ended up chucking the lot and the fuel already mixed up. Since started usaing correct marine 2 stroke oil no problems!

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