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mercury 50hp sound attenuator

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i have had several seasons with my 2009 pontoon with mercury 50hp running terrible. I've researched and tried several things.

symptom: will start when I push key for choke but most instantly fires and then whines down and dies. I can throttle up with prop in neutral and it will fire and run, but when I throttle to idle it immediately whines down and dies.

what I've done: siphoned gas and put fresh in. changed fuel filter, plugs. loosened gas cap thinking vent stopped up.

what i'm confused about: I know nothing about boat motors but what I've learned since owning this boat for five years and found this thing called "sound attenuator". on the one side of the piece there is two circle things and only one has a plug looking thing in it. it really looks like there should be a plug in both and i'm wondering if that's the case? I hope someone knows what i'm talking about.


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Mercury 50 hp 4 stroke EFI?

If so, your engine has an idle air control valve. It is a solenoid-activated valve with a hose on one fitting and the other fitting open to air. Should be found on the starboard side of the engine with the hose going to the intake manifold. The open fitting should cycle between vacuum and none as the motor idles. If so, ensure that: 1. valve is cycling and 2. the hose is still attached properly and not leaking.

The idle air control valve on the Mercury 40/50/60 EFI engines makes a 'paka paka' sound with the engine running. I don't think a faulty idle air control valve it will set a code or sound the audio alarm on those engines. Typically doesn't want to stay running below 1200 RPM, but operates properly otherwise above that RPM?

Believe the issue is with item # 6 in the link below.

Lastly, highly recommend not running ethanol based fuels with that engine. Running Seafoam and other quality fuel stabilizers helps too for keeping fuel fresh.



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Late to the party, but I had an issue with the AIC after a yearrly checkup/maintenance

The shop did install an update to the electronics and since then the AIC whistles. Or worse it sounds like a bunch of crickets....
Very annoying when at low speeds when escorting a sailing race as rescue RIB.

It appears that at low rpms the AIC takes in air at such a speed it whistles along the sharp edges of the top fitting.

Without breaking the part we now experiment with a piece of rubber hose as a muffler...

Any other thoughts?


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