yahama F4A 2003 4 hp outboard starting/running problems

[Snapdragon25]

Hi Folks
does anyone out there have any ideas why my outboard - Yamaha F4A 4hp 2003 is being a pain?

It will start relatively easy - doesn't require much choke, but then will not run properly, coughs and splutters, no rev range and just more or less stays on a very rough tickover no matter where the throttle is set!

If I then turn the fuel off or change it to the (unconnected) remote tank position it will start to rev up happily as it runs out of fuel. I have also had the same result if I drop the carb bowl drain plug out!

I have lost track of how many times I've taken the carb off and gone through all the usual cleaning procedures but there are no large lumps of debris emerging.

The throttle cable linkage and choke linkage all appear to be set up properly and the little air control screw doesn't appear to have any effect on the current problem.

The engine has been stood for about 12 months and prior to this it worked perfectly.

i've dropped all the jets out, cleaned them and had a wire up though the various orifices without finding any dead seagulls or likewise so I'm baffled at present!

Anyone got any bright ideas? Please!!

LB

 

[Balbas]

I assume its a 2T? What does the plug look like? Any indication it's fouling? Off the top of my head it could be the mixture is too rich, the oil ratio is too rich or its got a weak spark.

 

[Simonpk]

Old fuel? Same symptons as my strimmer has at the start of each year, if I bung in some new 2t fuel and it's fine.

 

[Snapdragon25]

Hi Simonpk and Balbas
The engine is a 4stroke so its not an oily problem and I've drained the fuel and replaced it already. Sparky looks as clean as a used plug normally does1 thanks for the input though! LB

 

[peteK]

Try a new plug if only to eliminate it.

 

[TQA]

Water in the fuel.

Drain tank passing the old fuel through a Baja filter. If you have water then the stuff that does not go through the Baja looks like this.

 

[Snapdragon25]

Thanks TQA for that but its regular fuel that I use in my car/m-bike and its not a problem. I must say your bottle full of stuff looks like a very generous early morning sample!
Regards