Engine making rushing air sound

[Herbieville]

Mercruiser 5.0 engines both make a rushing air sound at startup. The starboard engine calms down after about 10 seconds but the port engine never does. Engines both run fine with this condition.

I replaced the IAC but the problem did not go away after a day out on the water. The replacement IAC is borrowed and suspect, though.

Any suggestions?

Thanks!

-G

 

[Lazy Daze]

Is this a new thing, or has it always done it?

Could it simply be the sound of air being sucked through the throttle body? Does it calm down in relation to the RPM's dropping as the engine arms? What happens if you increase the throttle?

Please put your specs in your signature - it will help. Year, model, etc.

 

[Herbieville]

This is a new thing this year with the port engine.

Increasing throttle/RPMs doesn't seem to change anything.

Thanks!

-G

 

[flflatrate]

you are missing the iac muffler. if you pull the flame arrester off you will see a square hole where the muffler goes. the part is about a buck. get 2 and check and change other motor 2.

 

[Herbieville]

Thanks for the info!

Would you mind educating me on how the IAC, the valve and the muffler all interact mechanically?

Much appreciated!

-G

 

[coolings]

On my boat there was a part that has failed twice. I can't remember the name of it. Something like the startup valve. It feeds extra gas to the motor during startup. When the engine reaches operating temp, it should stop. When it is open, the engine will make a hissing type noise. With mine, I had problems starting up cold. It would take forever.