Why does an Evinrude airbox cover have two holes plugged

gjmsd

Petty Officer 3rd Class
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Oct 18, 2010
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83
I have a1975 Evinrude 135 and have always wondered why two of the fours breather holes have plugs in them. I'm thinking I should take them out to allow the engine to breath better. Anyone know why they are there and should I leave them in or remove them?
 

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oldcatamount

Lieutenant Commander
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Apr 4, 2010
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Re: Why does an Evinrude airbox cover have two holes plugged

Heck, if it were my motor, I'd take 'em out and see what happens.
 

boobie

Supreme Mariner
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Re: Why does an Evinrude airbox cover have two holes plugged

The plugs were put in those holes so you could pull them to get at the carb idle linkage. They also helped for airsilentsing. I always just pulled them and threw them away. This cover was also used on a mtr older than yours.
 

busted-bayliner

Petty Officer 1st Class
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Jun 6, 2010
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Re: Why does an Evinrude airbox cover have two holes plugged

i have the same on my motor except there are 3 holes an two are plugged so you guys say its safe to remove them?
 

63Sport16

Seaman Apprentice
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May 10, 2012
Messages
41
Re: Why does an Evinrude airbox cover have two holes plugged

Yes you can remove them if you want to. They were just access ports for Low speed idle adjustment.
 

busted-bayliner

Petty Officer 1st Class
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Re: Why does an Evinrude airbox cover have two holes plugged

assuming removing them would let more air in
 

nwcove

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May 16, 2011
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Re: Why does an Evinrude airbox cover have two holes plugged

the airbox with the plugs in will let your motor have all the air it should need, its not much more than a " muffler" to quiet the motor. they are designed to help keep water out of the motor in harsh conditions also.
 

emdsapmgr

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Dec 9, 2005
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11,551
Re: Why does an Evinrude airbox cover have two holes plugged

The airbox cover should have all 4 holes plugged-that's normal. These engines should be run with the airbox on the engine-and my guess is with those 4 hole covers in place. The engine is jetted to run with the cover on and probably with those holes plugged. Removing the cover itself, or the 4 hole covers will increase airflow somewhat to the carbs. Increased airflow without extra fuel could create a lean condition for the engine. It will get plenty of air through the existing large duct on the back side of the rear half of the airbox. Having said that, most of these older crossflows ran fairly rich on the old leaded gas that existed when the engines were made. Proabably would not have been a problem years ago. Not sure just what the impact would be using today's 10% ethanol fuels with those covers removed.
 

boobie

Supreme Mariner
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Nov 5, 2009
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20,826
Re: Why does an Evinrude airbox cover have two holes plugged

We're not talking about the old 90 * loopers here that required the air box cover to run. We're talking about a cross flow.
 
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