Yamaha 40hp ? dirty fuel

[reilly]

I have a Yamaha 40hp 4 stroke outboard running rough at idle and wont rev under load
I checked the fuel some crap in some black specs found
How do you clean out the jets I found three screws one on each carbi when I took them out there is a hole is this the ones I clean out
do i just ensure fuel is clean and continue to purge these screws
I went the long w/end without my boat and wont be till next Wednesday till someone will look at it so I have a go

[BaitThrower]

I'd start by grabbing a bottle of "Fuel Doctor" from Supercheap Auto or Autobarn. Add a bit to your tank and each time you fill up. This will break down any contaminants in the fuel and help clean your jets. May not solve the problem now, but it will help stop it occurring again in the future :)

[foxx510]

The screws you want to drain the carbs with are at the bottom of the carb float bowl and will probably have a little drain tube/hole coming off near the screw. Other similar looking screws will be mixture screws and should be avoided. If there is crud in them though they probably need removal and a proper clean with a compressor.

[backlash08]

check the spark plugs with those symptoms
cheers - Craig

[foxx510]

Yep, plugs are cheap and easy to replace, may as well eliminate that one first. It was the cause of the same problems on our motor a few weeks ago. Plugs looked new, but one was faulty.

[Moonlighter]

Hi Reilly

One thing that I'm surprised that no-one has mentioned is the need to prevent the same thing happening in future: install a good quality water separating fuel filter and change the filter element every 12 months. They are much more affordable now, and will help save all this grief from dirty fuel (if that is the problem) in the future. Even if its not the problem this time, its a good idea to fit these filters anyway.

Also you need to be sure that the contamination is not coming from your "fuel system" - meaning that you need to ensure that the inside of your fuel tank is not corroded etc, that all your fuel lines are in excellent condition and not degrading/breaking down, that the fuel connectors are all good. If in doubt, replace.

Best of luck!!

ML

[pursuit001]

hi mate a fuel filter is the best thing to fit to prevent this as others said as to pulling it apart yourself spend the couple hundred to get it done rather than doing it yourself as you may be digging deeper in your pocket to repair it if somethink goes back in the wrong way

[reilly]

I removed the drainage screws nil foreign matter in them blew out with compressor to just make sure.

I got a friends Yamaha tank and fittings and flushed the system with his fuel after checking it no change.

I have disposed the old fuel and flushed out my tanks

I wont go any further with fuel system as this is the limit of my experience.

Going to remove all the high tension leads and ensure they are dry as well

I went to remove the plugs haven't got a socket to fit all mine are to thick will need to get one and I will replace the plugs tomorrow anyway.

I like the four stroke but miss the simplicity of the old 40 1992model two stroke.

(http://www.reference.com/search?q=Simplicity)

[reilly]

Thanks moonlighter
I am sorry I didn't deal with prevention before getting this problem
You hit the nail right on the head no excuse just lazy I guess
Once bitten twice shy

[captain rednut]

hi check your engine oil now and see if its higher than normal as this model engine has a history of faults with the carbys they dont like dirty fuel, causes the fuel to enter the sump causing diluted oil and than they could give more severe problems. cheers jim