[njc15880]

That is extremely helpful. So that K&N flame arrestor/filter will fit in place of the stock flame arrestor?

[Hudson River Steve]

Take off the plastic cover and the flame areastor attaches to the round throttle body with a simple hose clamp.

[Oregondunes]

I have the K&N model. It still whistles

[Motoxxx43]

That sound is normal. That is a big motor and it requires a lot of air (and fuel!). If you were to modify your pickup trucks air intake to a straight pipe and filter it would sound the same while operating under load. That whistle sound is air moving through the throttle body. I kinda like that sound...

[Motoxxx43]

I forgot to mention why I used a pickup truck as a comparison: To meet emissions standards they have to operate under a certain decibel limit therefore they put the sound chambers on the factory plumbing. Without those chambers the motor can actually be heard breathing!

[Hudson River Steve]

To be clear, my 7.4 MPI does not whistle at cruising speed...it only whistles on deceleration when coming off plane.

[njc15880]

So I am revisiting this problem. I installed the filter that you recommended and the whistling did not stop. I even ran the boat with nothing on the throttle body at all. I am running low on ideas. I have narrowed it down to the throttle body I am pretty sure. Im thinking that the air moving through it is creating turbulence and causing the whistle. Is there a throttle body spacer that would work to see if that may be causing the issue?

[Oregondunes]

Mine whistled the same way. It's air rushing Over and thru the throttle body. Normal. You could always run a straight hose to yur engine bay vent