Grinding Motor Noise - New Info....

[makolab]

Awhile ago I posted a strange gringing sound from the engine of my boat. Its a 2006 5.7l 300hp mercruiser in and the sound seems to be coming from the flame arrestor area near the throttle body. As i searched other forums, someone descibed the EXACT noise as:
"a very loud suction noise that varies with the rpm's (example: as I stop the boat and put it in neutral, the hissing is not as loud as when the engine is revving...you can hear the suction dissipate as the engine slows, but it never stops and is annoying and loud."

Thats my exact problem!! Is anyone familiar with the vacuum lines near the TBI? The motor runs fine throughout the RPM range but its loud and annoying. Sometimes she will stall when cold start but after she is warm, she idles fine. Any vac. experts?

[Laidback]

'Grinding' or 'gringing' or 'suction' noise , suggest take off aircleaner, check all the hoses for a hole/s, clean the filter element. Check the inlet manifold for cracks, loose nuts. (Unlikely that the manifold gasket is faulty - but it is possible, leave this check to the last)