Testing Carb Emulsion Tube for Leakout


Petty Officer 3rd Class
Sep 18, 2008
The carb of my 1998 30 horse Johnson BJ30BAECS is leaking fuel from the air intake area. A repair manual says that the emulsion tube could leak and tells almost everything I need to know to test it, but not enough. As seen in attachment here of the text about the leak issue, a syringe is to be filled with alcohol and the idle circuit is to be filled with the alcohol with the carb inverted and any leaks seen then repaired with a sealer. But it doesn't say where the idle circuit is, and exactly where to inject the alcohol. The typical carb in the books illustration is very close to my carb which is pictured next to the book's text about the emulsion tube, so the testing instructions should apply to my carb. Might anyone know the exact location of where the alcohol is injected in the carb, and where the idle passage circuit is in this style carb?


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Rear Admiral
May 4, 2004
Remove the idle adjust screw, (but first note the setting) and fill the idle circuit with propanol via its position .... maybe ?
(Or, if you really think its leaking there, clean it free of oil with propanol and put a very tiny drop of Ultra lock or red Loctite there anyway)

If you have fuel leaking from the air intake you should direct your attention towards the float and needle valve.
Check the float height but don't mess with it unless it's obviously wrong.
Inspect, clean or replace the needle valve and seat.

Finally, throw away the Seloc manual and buy a copy of the Official OMC manual from Outboardbooks.com
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Sea Rider

Supreme Mariner
Sep 20, 2008
When primming the fuel bulb with arrow pointing upwards till firm, is there fuel spills seen around the carb ? If so, could be due to needle/seat gunked, bad float adjustment or middle carb's gasket shot or even a combo of the 4 mentioned issues...

Happy Boating