Air Silencer

[fsutim]

I purchased a 1978 70HP Johnson about a month ago and does not have an air silencer, what is the air silencer for and is it needed for propper engine operation?

 

[rickdb1boat]

Re: Air Silencer

Exactly what is says. It silences the intake howl from the carbs. Some motors will not run right when it's removed. Others, it don't matter! My 89' 28 HP Johnson doesn't have one, but my 91' 70 HP does. I've never run it without it, so I really can't say if it makes a difference in the way it runs. I doubt it!

 

[R.Johnson]

Re: Air Silencer

The air silencer is just that! an air silencer, Without it you will hear a high resonense noise, such as the reed valves snapping shut. On some engines, running without it can cause a lean fuel mixture at full throttle.

 

[Chinewalker]

Re: Air Silencer

Some air silencers are actually serving two purposes. One is ti quiet the motor, and two is to act as a bit of a n intake tuner. There are pressure waves created when the motor is running and the placement of a flat surface in front of a carburetor can actually create a minor super charging effect. It's not super significant (say 60-100 RPM at wide open throttle)) but it is tangible....<br />- Scott

 

[rickdb1boat]

Re: Air Silencer

Chinewalker <br /><br />Thanks for the explaination. Sounds good to me. I really didn't know if it made a difference or not. I've heard that on some motors, if it's not in place, it will not run right.

 

[AUGIDAWG]

Re: Air Silencer

Chinewalker is right.<br />When a two-stroke draws a pulse into the intake, it sends a reverse pulse wave back.<br />If you place a plate in front of the carburator intake, you can bounce yet another pulse wave back into the carb.<br />You can tune at what rpm this has an effect by the distance from the plate to the carb.<br />It doesn't help that much, but it is measurable.