Mercruiser 496 HO MAG intake noise

[timandheidi2]

Getting a crazy noise from my newly installed 496. Previous owner of the engine said it is normal. This noise is coming from the intake, and sounds like darth vader breathing. What is your guys input? here is a link to a YouTube video. This is not my video or my engine. But is doing the same thing. https://youtu.be/C4O8c4pg9ek

 

[harleyman1975]

Idle air control muffler?

 

[timandheidi2]

Not sure. I will do some checking on that. Thanks

 

[Scott Danforth]

you have 496 cubes of engine trying to breath thru a little air cleaner.

you should hear them at full throttle, you can hear the air whistle over the throttle blades

 

[timandheidi2]

So, remove the KandN?

 

[Scott Danforth]

K&N not worth it in this application

this is from OSO and is a very good read on air filters. Discusses a 502 build and runs it though several pulls just to get data on changes. Even got into fuel causing some real issues from one vendor to another.

http://www.offshoreonly.com/forums/g...n-my-shop.html

 

[timandheidi2]

you have 496 cubes of engine trying to breath thru a little air cleaner.

you should hear them at full throttle, you can hear the air whistle over the throttle blades

Live with it? Or what do you recommend

 

[alldodge]

To me that sound is not normal, it should not be going up and down. Are the rpm's fluctuating or staying constant?

K&N won't help but with your stock motor won't hurt.

 

[timandheidi2]

To me that sound is not normal, it should not be going up and down. Are the rpm's fluctuating or staying constant?

K&N won't help but with your stock motor won't hurt.

Rpms are staying the same. Runs great.

 

[bman440440]

IAC opening and closing?

 

[timandheidi2]

Could be, but is it normal

 

[alldodge]

Could be, but is it normal

Never heard one do that, an EFI motor should be constant at a steady idle. It could be the IAC, but what is causing the IAC to change to keep the motor at a steady idle would be my question

 

[timandheidi2]

Never heard one do that, an EFI motor should be constant at a steady idle. It could be the IAC, but what is causing the IAC to change to keep the motor at a steady idle would be my question

My thought exactly. Previous owner said it has done this since he has owned it. I have rode in other 496ho mag boats and have not heard this noise. I will start throwing parts at it.

 

[alldodge]

I will start throwing parts at it.

I wouldn't suggest that, I would suggest getting the motor scanned for codes. It might be a loose connection on the TPS, IAC, MAP or other. The scanner will show if there is something out of spec

 

[Scott Danforth]

could be cyclical fuel pressure and the ECM is compensating by adjusting the IAC.

find out what is wrong prior to buying any parts.

 

[timandheidi2]

I'll do some checking this weekend. Thanks guys