evinrude running probs????

[Frank mellin]

Have posted several threads about my 14hp worktwin engine previously but problems persists.
Basically only starts using easistart will then run for about 30 seconds before dying as if choked up.
Fuel mixture ok.
Have fitted new vacuum fuel pump, had carburettor apart twice and everything seems clean and serviceable, float mechanism working ok and jets clear.
obviously spark must be ok as it does run albeit for 30 seconds.new stator fitted. and new plugs.
Compressions seem ok
I am really at a loss to know what to check next.
It seems like fuel problem but when I remove carb it full of fuel.
Is it possible that the carb is using fuel quicker than it receives it,
If so what could cause that.
Is there any way to check the vacuum being created as this drives the pump.
would really appreciate if anyone can assist as I am losing the will to live!

 

[BruceK]

re checking vacuum pump. Remove fuel line to carb from pump. Dribble in a teaspoon of fuel direct into the carb intake. Start her throttle wide open (she should start first or second pull) and note if the pump pumps fuel. If it does then you need to check choke and pilot jet screw.
I'm assuming float levels are correct.
Have you had the carb cleaned ultrasonically? It may be worth your while for instance aluminium salt deposits can block internal passageways such as from carb bowl to pilot jet etc if it has been left with fuel in for long periods in damp weather.

 

[Frank mellin]

re checking vacuum pump. Remove fuel line to carb from pump. Dribble in a teaspoon of fuel direct into the carb intake. Start her throttle wide open (she should start first or second pull) and note if the pump pumps fuel. If it does then you need to check choke and pilot jet screw.
I'm assuming float levels are correct.
Have you had the carb cleaned ultrasonically? It may be worth your while for instance aluminium salt deposits can block internal passageways such as from carb bowl to pilot jet etc if it has been left with fuel in for long periods in damp weather.

thanks for the info very useful. Have done what you suggested and pump is working fine which suggests that the problem is in the carb.
just wondering if I have missed something when checking it. The main jet is definitely clear but not sure if there are any other orifices that I may have missed.
will get the carb cleaned professionally as you mention.
Thank you.

 

[Caraway]

If the float chamber is full but fuel is not getting to the cylinders you have a blockage. The jelly that fuel forms can restrict flow in any passage in the carb. It needs properly cleaning. At least with a carb cleaner soak and a thorough blast with an air line.

I haven't been keeping up with this. Is there an inline fuel filter tucked away somewhere? I had a Mariner with a small filter underneath the power head which was restricting the flow of fuel to the carb. Once the fuel level has dropped in the float chamber so that it is not at the correct level in the jet the running will suffer.

 

[trevbouy]

Is there an emulsion tube as part of main jet or is it seperate? I had one with seperate emulsion tube which I didn't realise. Suffice to say that was blocked.

 

[Frank mellin]

If the float chamber is full but fuel is not getting to the cylinders you have a blockage. The jelly that fuel forms can restrict flow in any passage in the carb. It needs properly cleaning. At least with a carb cleaner soak and a thorough blast with an air line.

I haven't been keeping up with this. Is there an inline fuel filter tucked away somewhere? I had a Mariner with a small filter underneath the power head which was restricting the flow of fuel to the carb. Once the fuel level has dropped in the float chamber so that it is not at the correct level in the jet the running will suffer.

havnt been able to find a filter but i did wonder about the fuel level in chamber.
I have now eased the float assembly so that it does not cut off fuel supply as quickly as it shut off supply with very minimal movement.
will see if that helps.
many thanks

 

[Frank mellin]

Is there an emulsion tube as part of main jet or is it seperate? I had one with seperate emulsion tube which I didn't realise. Suffice to say that was blocked.

I have no idea what the emulsion tube looks like so you could be right.
I will check on line to see if anyone has a picture of this carb in pieces.
Many thanks

 

[trevbouy]

Main jet is longer with cross drilled tube on it.
Or
Main jet is plug like and below it is a seperate tube which either can be pushed out with finger from carb throat or a sharp knock onto a piece of wood to jar it out.

 

[Frank mellin]

Main jet is longer with cross drilled tube on it.
Or
Main jet is plug like and below it is a seperate tube which either can be pushed out with finger from carb throat or a sharp knock onto a piece of wood to jar it out.

ok its the second option thanks. will take it out and check.
appreciate your help,thank you.

 

[BruceK]

if it's not idling it's pilot needle and jet. With the carb out looking from the engine side. Right in front of the butterfly is a small hole maybe 0.5mm that feeds fuel to the engine when the butterfly is closed. That jetting will clog up and provides fuel for the first 20 to 30% of the rev range, after that the main jet comes into play. Also in front of the butterfly on the top usually are choke ports for fuel enrichment. If they are dribbling loose you have problems. Finally never forget the carb manifold gasket. If air is leaking past the carb it will never run right.

 

[Caraway]

You haven't actually said if the needle valave is working OK. Have you tried blowing through the fuel delivery pipe on the float chamber top and holding up and releasing the needle valve. Some with rubber tips can jam and those with ribs down the dide of the needle can rilt and jam if worn. They are eyewateringly dear to replace.

 

[Frank mellin]

if it's not idling it's pilot needle and jet. With the carb out looking from the engine side. Right in front of the butterfly is a small hole maybe 0.5mm that feeds fuel to the engine when the butterfly is closed. That jetting will clog up and provides fuel for the first 20 to 30% of the rev range, after that the main jet comes into play. Also in front of the butterfly on the top usually are choke ports for fuel enrichment. If they are dribbling loose you have problems. Finally never forget the carb manifold gasket. If air is leaking past the carb it will never run right.

Have now got the engine to run for longer after fitting new pump.
It still runs rough though as if misfiring and is very lumpy.Revs up ok.
As have fitted new stator and plugs and tested coils etc just wondering if problem could still be carb or whether it is more likely electrical.
Is there any way to test the strength of the spark with the motor running using a multi meter.
Some posts talk about points adjustment but I dont think this engine has any points?
Am also going to check the compressions to make sure they are ok although have been advised that they were.

 

[BruceK]

Lumpy? as in gurgling rich? That would explain why it revs up easily but dies.

Electrical? Run it in the dark and see the HT leads and supressor caps arent arcing to the body. Old HT leads and caps can build up a carbon leader.

 

[Frank mellin]

if it's not idling it's pilot needle and jet. With the carb out looking from the engine side. Right in front of the butterfly is a small hole maybe 0.5mm that feeds fuel to the engine when the butterfly is closed. That jetting will clog up and provides fuel for the first 20 to 30% of the rev range, after that the main jet comes into play. Also in front of the butterfly on the top usually are choke ports for fuel enrichment. If they are dribbling loose you have problems. Finally never forget the carb manifold gasket. If air is leaking past the carb it will never run right.

thanks for your advice.Can see hole in chamber next to butterfly flap but how to check if blocked?
there is a round metal disc on casing above this hole which I presume if removed will enable cleaning.
I have just got a carb kit and I notice that this disc is supplied.
How do I remove old disc and more importantly how do I install new one so that it is airtight.
Any advice would be much appreciated.

 

[BruceK]

I doubt it's for access. If the pilot passage ways are blocked carb cleaner and compressed air and failing that an ultrasonic clean. I suspect but cannot be sure what you are seeing above is the choke porting

 

[Frank mellin]

I doubt it's for access. If the pilot passage ways are blocked carb cleaner and compressed air and failing that an ultrasonic clean. I suspect but cannot be sure what you are seeing above is the choke porting

 

[BruceK]

Ah OK passage way access. Part 22 and it's passageways is what I am concerned about and the choke lever assembly

https://www.boats.net/catalog/johnson/outboard-by-hp/15hp/15el77m-1977/carburetor-amp-manifold

 

[Frank mellin]

Is there an emulsion tube as part of main jet or is it seperate? I had one with seperate emulsion tube which I didn't realise. Suffice to say that was blocked.

Can you explain how the emulsion tube works.it seems to have a hole through it the same size as the jet.also it has tiny holes in the side in the chamber.not sure what for as surely fuel will take the least line of resistance directly through the main jet and out of the top of the emulsiuon tube

 

[Caraway]

Don't get sidtracked into carb design. If the emulsion tube is clear and the small holes are clear, look elsewhere.
Best bet is to get a different carb and try that. Borrow or buy a s/h one. Or get an outboard mechanic to look at it. You are going around in circles.

 

[Frank mellin]

Don't get sidtracked into carb design. If the emulsion tube is clear and the small holes are clear, look elsewhere.
Best bet is to get a different carb and try that. Borrow or buy a s/h one. Or get an outboard mechanic to look at it. You are going around in circles.

Ever decreasing ones at that,likely to disappear somewhere soon.
I think your right, will seek advice from mechanic.