whistling noise from engine when reduce rom from 4600 to 3500

[R.N.]

Hi ,
Can anybody give me some ideas why there is an engine whistling when i reduce the rpm.
It doesnt seems to have any escalation over time , runs fine at any rpm .
Belts are fine (new and seems to have the right tension)
Engine is the volvo penta 5.7 gs plkd with original spark arrestor .
Thanks

 

[Silverbullet555]

Some volvo penta do it. My 5.0gxi didn't do it. My 8.1gi sounds like a turbo.

 

[Scott Danforth]

Its the secondaries closing as you back off the throttle. Common on carbed motors.

Normal

 

[Maclin]

A Holley 4bbl will sometimes make a whistling noise when backing down from full throttle to half or 3/4 throttle as the secondaries vacuum can reacts. It only lasts for a second or two, and changes pitch as it goes away though, not constant.

 

[R.N.]

Great news. thank you .