How well should a 'Rude 140 idle?

I've got a new-to-me 1984 'Rude 140 on my latest project boat. Someone before me removed the oil tank and blocked the oil line so I'm running pre-mixed gas. I've put new plugs in it (UL77V as per the factory manual), I went through the link-n-synch procedure, the reeds look good (had the intake off, so I was definitely able to see the reeds), compression is good (around 120 on all 4), temperatures are good (new thermostats, 140 F at idle on both sides and around 125 F at speed on both sides), spark for each cylinder jumps at least a 7/16" gap at cranking speed. The prop is well matched to the boat (5500 rpm WOT). While warming up it sneezes some, but after it's run awhile that goes away. Once off idle the engine runs great, but at idle it runs like an old tractor.

Is it even possible to make this engine idle smoothly, or is it always going to be a little cantankerous?

I have a 1980 115, same basic motor. Mine wouldn't idle worth a damn until I swapped out carbs.. the old ones were worn physically out, and sucking air through the butterfly shaft holes. Now it starts great, and will idle for hours.

One of those motors will run very smooth at idle .----Will idle all day long too if it is in good condition.

Sneezing is usually caused by a lean fuel condition in the fuel system. Carbs ??

Boobie said:

Sneezing is usually caused by a lean fuel condition in the fuel system. Carbs ??

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Yep, but it only sneezes until it warms up. After that it's fine (well, not fine but at least it quits sneezing).

I guess I'll go ahead and rebuild the carbs sometime this winter.

check the ethanol level in your fuel, if it is over 10%. there you go. 80's engines were made with little tolerance to ethanol

http://www.wholesalemarine.com/tester-fuel.html?gclid=CJHQ-PW-t8ECFWVp7AodaE8AJw