Hissing sound from motor

[family time]

I have a 1999 Sunsetter with the indmar motor and last week on the lake the motor started making a hissing sound. The higher the RPM on the motor the louder the sound. I lifted the motor cover but was unable to pin point the sound. It sounded like air escaping from the motor. The motor seemed to run fine and all gages were ok.

[tvano]

my money says that it is the air rushing into the throttle body. normal.

did you remove the flame arrestor (think where the air filter would be).

has it rattled loose?

on my response it's much more noticeable from behind the dog house.

i would take a few minutes to look under the dog house to insure that nothing is misplaced then relax.

if this is a new behavior it might be worth a bit more effort but i can't imagine what comes next.

[JeffS]

In my experience - only two things to check. Find a friend who smokes, get a couple of cigarettes.

You need the smoke.

You probably have either:

an exhaust leak where the manifolds connect to the block - or where the manifolds attach to the riser...

Or...

An intake gasket leak - air getting in somewhere that it's not supposed to be - somewhere on the intake manifold side of things.

On a calm day, or in the garage on your fake-a-lake. Put the engine at fast idle just shy of 2,000rpm.

Blow smoke along the exhaust components and intake components - you'll see the smoke move in or out and the leak will be obvious.

Repair or replace that component/gasket - and I bet you'll be all good.

[Sixball]

I am going with the throttle body. Clean your spark arrester. Or the other thing check and see if your PCV valve got knocked out or the rubber grommet is lose or part way off. A new PVC is cheep and you can get one at NAPA or any auto parts store.

[RTS]

I am going with the throttle body. Clean your spark arrester. Or the other thing check and see if your PCV valve got knocked out or the rubber grommet is lose or part way off. A new PVC is cheep and you can get one at NAPA or any auto parts store.