Please diagnose my engine problem (video)

[gwoloshyn]

1966 Evinrude Ski twin 33hp model no. 33653

I'm having a problem with my motor idling, once it gets down to lower RPM's it starts to do this. I just cleaned the carb completely so that's not the problem. Carb needle settings are stock. It has good compression too with spark in both cylinders. New spark plugs. Does anyone have an idea what the problem is? Maybe points/condensors need a tune up?

http://www.youtube.com/watch?v=wpzIW0dE8oA

 

[lindy46]

Re: Please diagnose my engine problem (video)

Did you rebuild the carb with a new kit? Remove the welch plug on top and clean the idle circuit beneath?

 

[oldcatamount]

Re: Please diagnose my engine problem (video)

It seems to stumble, recover, stumble, recover, rather quickly which would lead me to believe it's an ignition issue rather than fuel related. If it's been awhile since the ignition has been serviced, then I would suggest replacing the points, condensers and the plug wires. Look at the coils when replacing the plug wires for cracks or discoloraton.

 

[wilde1j]

Re: Please diagnose my engine problem (video)

What with the "stock" needle sttings? There's no such thing ... there right and not right, determined by adjusting for correct running, not to any pre-determined setting.

 

[gwoloshyn]

Re: Please diagnose my engine problem (video)

Did you rebuild the carb with a new kit? Remove the welch plug on top and clean the idle circuit beneath?

Yes, I installed a new carb kit and I think I blasted out the idle circuit, but I'm not sure what that is. Is it the channel that the low speed needle screws into and has a few small ports leading out into the main channel?

The motor was sitting for a while so I don't believe the ignition was ever serviced. I plan on replacing some ignition parts soon. Thanks

 

[gwoloshyn]

Re: Please diagnose my engine problem (video)

I removed the flywheel and checked the coils and everything looked new, no corrosion or discoloration anywhere.

Is there a way to remove the welch plug and reusing it or will I need to drill a hole in it and have to buy a new one?

 

[JDusza]

Re: Please diagnose my engine problem (video)

gwoloshyn,

There are 2 paths for fuel to take in the carburetor; high speed path (circuit) and low speed path (circuit).

The low speed jets are located beneath the Welch plug. They are small holes machined into the carb casting and sealed with the plug. They are visible in the carb venturi, on the top side at the throttle butterfly. I am not familiar with this specific carb, but usually there are 3 small holes of different diameter. These need to be clean and unobstructed.

Use small diameter wire or torch tip cleaning tool to clear. You are better off removing the plug rather than trying to clean from the venturi. If there is junk beneath the plug, it can relocate to the jets after cleaning and reclog.

The Welch plug is not reusable. A new one usually comes in the carb rebuild kit.
To get it out, drill a small hole and pry it out with a small screwdriver or similar tool, being careful not to drill into the carb casting or chipping the casting edge as you pry it out.

To replace, locate it, get a punch of slightly smaller diameter and flatten the new plug into place with the punch.

Before you go there, another easy check of the ignition is to run the engine in the dark looking for random arcs and sparks to grounds; wiring, leaking at connectors, cracked coils, etc...

Good luck!
J