Yamaha 140HP 2 stroke 1994model stalls

[kix766j]

Hi,

last year i bought a boat with a Yamaha 1994 2 stroke engine 140HP (the navy blue ones). It always worked pretty well for me but lately it's been switching off unexpectedly.
Engine is saltwater BTW.

I noticed that it goes off mainly when it is still pretty cold after about 5-10mins from starting it up. When it goes off it takes about 2 minutes of trying to start it up again to start... and after coughing everytime during those 2 mins, it starts up and works flawlessly until the next time it gets cold again.

I also noticed, that lately it wouldn't start up as easily as it used to if you leave it for about 3-4days without starting it up... basically it takes 2-3turns to start up now, whilst before it used to start up immediately or on the 2nd start...

The water coming out of the engine is always pretty cold and considering this happens when the engine is still 'cold' i doubt it is an overheating problem.

Mechanic just serviced it a couple of weeks ago and changed fuel filter, spark plugs and greased engine.

Any tips or ideas on what the problem may be? I am not a mechanic but can do some basic troubleshooting myself.

help is appreciated
thanks

 

[rodbolt]

Re: Yamaha 140HP 2 stroke 1994model stalls

sounds like a pilot fuel jet clogging in the carbs.
dissaemble and clean the carbs, usually you can get by with just replacing the fuel bowl gaskets.
the 140 is a non US market motor so I assume your not in the continental US.

 

[kix766j]

Re: Yamaha 140HP 2 stroke 1994model stalls

hi rodbolt and thank u for your reply,

yes u r correct, i'm from Malta (Europe), a small island in the middle of the Mediterranean.

Yesterday i took out the boat for a spin to get some more info on this issue.
After about 5-7mins of driving at 3300rpm it started knocking faintly... i increased it to 4000rpm and it continued working normally again. I then put it back down to 3300rpm and continued driving for another 15mins without any problems.

So basically, this issue is when the engine is still pretty cold (within 10mins of starting) and revs between 2800-3300rpm. above those revs its fine.. below those revs it rarely stalls (although it did it once or twice to me but not that frequent)

will i be able to disassemble the carbs and replace the fuel bowl gaskets myself? i consider myself to be a beginner but i purchased a Yamaha Outboard full service manual 2-250HP 1984-1996 from ebay which should be able to help me out. i am a computer technician and could give it a go but if it is out of my league i'd rather leave it up to a mechanic who knows what he is doing..

thanks for your help

 

[rodbolt]

Re: Yamaha 140HP 2 stroke 1994model stalls

its not difficult at all.
usually I dont remove the main or pilot fuel jets a soak the bowl in carb cleaner and then spray them out with carb claener in a can.
spreay carb cleaner through the pilot air jets while watching the pilot fuel transfer tube.
wear eye protection as carb cleaner will hurt like Hades and temporarily blind you if it hits your eyes.
if it hits your eyes drop to your knees, DO NOT RUN BLIND.
dont ask .

 

[kix766j]

Re: Yamaha 140HP 2 stroke 1994model stalls

thanks for your replies.

i will wait to receive the service manual and try this out myself and repost once its done... probably sometime next week.