Outboard help required please...

seamaster30

seamaster30

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Joined
11 Aug 2007
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257
Location
Ireland
www.marina.ie
Hi,
I have an old 2 stroke 4HP outboard (with gears - sorry I don't have the number with me right now poss a 4AC ?)
It starts easily, and runs with the throttle open, but at tickover I need to play with the choke to keep it running.
I have cleaned out the fuel tank and filter, refilled with fresh fuel, cleaned the carburettor. I have also adjusted the slow running 'idle screw' and checked the spark plug.
I understand from the symptoms it's likely to be a blocked slow running (idle) jet, but I am not sure where to find this - I didn't see anything obvious other than the main jet, and the hole the idle screw goes into was clear - can anyone help identify where/what I should be looking for?

EDIT - Yamaha make /forums/images/graemlins/smile.gif

Brian.
 
A new plug is always a sensible first thing to try (you carry a spare i guess so try it) but if you can keep it running by playing the choke it is almost certainly a partly blocked carb jet.

You can access parts diagrams back to 1984 at http://www.yamaha-motor.com/outboard/service/servicehome/home.aspx. But if much older the carb design may be different.

Sometimes difficult to clean carb jets without poking something through but it must be something that will not damage them. I use a piece of soft copper wire when necessary.
 
Sit up at the back there and stop lolling about. Now, see here.....

Almost certainly the idle jet is blocked still. What often happens with outboard carburettors in a marine environment is that crystalline oxides form inside the jet ways. I don't mean inside the JETS but the jetways. If you look closely at the carburetter you'll see what looks like half-round tubes formed into the body casting. These are the jetways. In all cases one end of each of these tubes will either terminate in a jet, or in what looks like a ball bearing pressed into the end of it, which it is. Digging out the ball bearing (don't bother to save it) will reveal a hole bored through. This will terminate in either a jet orifice or intersect with another jet way. It is these jetways which can become completely obstructed.

The solution is this, prize out all ball-bearings, remove all jets. Carefully re-drill each jetway, blow out all the crud. Get a little piece of plumbers solder or soft lead, (small fishing shot will do if old lead ones,) and hammer a small piece of lead into the hole where once the ball bearing resided with the round end of a very small ball pein hammer to reseal the jetway. Replace all jets. Job done, it will now work like a dream.
 
Thanks guys, much appreciated - this will keep me occupied during the long evenings until the weekend /forums/images/graemlins/smile.gif
I wondered what the 'ball bearings' were, but didn't want to force them out.
/forums/images/graemlins/smirk.gif /forums/images/graemlins/smirk.gif
 
[ QUOTE ]
Sit up at the back there and stop lolling about. Now, see here.....

Almost certainly the idle jet is blocked still. What often happens with outboard carburettors in a marine environment is that crystalline oxides form inside the jet ways. I don't mean inside the JETS but the jetways. If you look closely at the carburetter you'll see what looks like half-round tubes formed into the body casting. These are the jetways. In all cases one end of each of these tubes will either terminate in a jet, or in what looks like a ball bearing pressed into the end of it, which it is. Digging out the ball bearing (don't bother to save it) will reveal a hole bored through. This will terminate in either a jet orifice or intersect with another jet way. It is these jetways which can become completely obstructed.

The solution is this, prize out all ball-bearings, remove all jets. Carefully re-drill each jetway, blow out all the crud. Get a little piece of plumbers solder or soft lead, (small fishing shot will do if old lead ones,) and hammer a small piece of lead into the hole where once the ball bearing resided with the round end of a very small ball pein hammer to reseal the jetway. Replace all jets. Job done, it will now work like a dream.

[/ QUOTE ]

Dont mean to be contradictive but forget all that ball moving stuff and just boil the carb (after removing all the gaskets/seals etc) in a small sauspan for an hour or two and it will remove any crud from all these passageways along with any varnish that has formed over the years, its worked for me every time in the past.
C_W
 
I find clogging of the carburetor jets on my 4hp Yamaha a common problem, despite filtering the fuel through a coffee filter when topping up the tank.
The carburetor needs cleaning about every 3 months. (My previous 8hp yamaha never had a carburetor clean in its 15 year life !)
I just blow (unleaded fuel is good for you) and stick a needle gently up the main jet.
Works every time. I can now do it in about 10 min.
 
Boiling does not always work m'dear, and remember, you are trying to remove the encrustations via a small hole. My way is more engineering it's true, but success is always guaranteed.
 
Just to put you all out of your misery... /forums/images/graemlins/smile.gif
Cliveshep's method worked a dream - I have a nice slow tickover, and it pops into gear without stalling.
I found I could work a strand of soft copper wire into most places without removing the balls though and it worked a treat - so perhaps it was not as bad as it might have been.
A cracking evenings work - thanks to all for your suggestions.
 
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