How big should the hole be in Idle Jet/Orifice?

1975 Evinrude 135HP. 135589E Spark and compression are all good. WHen you advance it above idle it runs like a dream. Just in the 700-900 range rough, coughing bucking spitting. Its still Idling really rough and dumping a little fuel from the carb after it runs. When I restart I have to advance about half way and get a big puff of smoke. Seems Like its getting too much fuel... Just checked the floats and the needle valves all is clean and functioning properly. all the orifices are clean as a pin. but im thinking maybe over time with who knows how many cleanings with wire and who knows what being jammed through them, the hole could be wallered out over time - giving more fuel that it needs at idle. I ran a .028 piece of guitar string thru them (idle orifice) with room to spare. Is that too big?

The idle orifice is supposed to be a #30.. I'm guessing that is 30 thou, but I could be wrong. Better to pull it and read the number on it. Check for play in the butterfly rods through the carb bodies. Over time the holes will wear and mess up the idle and low speed running.

Thanks! Ill check it out.

Yes, the imprint on the side of the jet (if it states 30), that indicates a ID of .030 .

Some of those old engine require that the jets are either drilled out or replaced with .031 . DO NOT exceed the size of .031 as that will cause the engine to flood out.

With the carburetor face plate removed, observe the carburetor throats as you pressurize the fuel primer bulb. If fuel flows out of any portion of the carburetors, they will require cleaning and rebuilding.

Thanks Joe Ill check that out...if I can quit fishin long enough for the boat to sit still.

Progator135 said:

Thanks Joe Ill check that out...if I can quit fishin long enough for the boat to sit still.

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If it's running that good, the jets must be fine.

What about spitting gas from the air orifice above the throttle? It seems to run fine other wise. Cleaned carburetors. Floats are right.

JamesRo said:

What about spitting gas from the air orifice above the throttle? It seems to run fine other wise. Cleaned carburetors. Floats are right.

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James.... This post is over 6 years old... ignore it.

@ Joereeves: based on the below, wouldn't be the other way around? the bigger the Jet the more air causing a leaner condition?

"Some of those old engine require that the jets are either drilled out or replaced with .031 . DO NOT exceed the size of .031 as that will cause the engine to flood out" .