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scttmzr

Mercruiser 350 Magnum MPI Black Scorpion Air Idle Valve

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scttmzr    2

From what I've read online it seems that my 2005 Enzo SV230 has all the symptoms of a failed Idle Air Valve (IAV). It stumbles around idle coming out of gear quite often and sometimes even dies, and the only way to get the engine to start when its hot is to give it neutral throttle. After some reading online I ordered the Standard Motor Products AC423 Idle Air Control Valve of Amazon for $40 (In comparison to the $178 for the OEM Mercruiser 866326) which is supposed to be a direct replacement. Multiple people on Amazon said it worked perfect on their Mercruiser 350 Mag MPI so I figured it should work on mine! Of course when I received the part and went to install it I found a couple things that I'm not so sure about:

  1. The original part I removed (assuming it is OEM) does not appear to have a pin and spring in it that the new replacement part has. Anyone know the function of this, or if it is of any concern?
  2. The replacement part came with a small rubber gasket that is definitely not correct for this application; it appears as though it should be used in an application that has a machined groove more like an o-ring would have. After searching for the correct gasket online, all I seem to find pictures of is a simple thin sheet style gasket that is cut to the profile of the valve. The gasket I removed from the boat was pretty thick and is overmolded on a mesh screen material. I'm wondering why this screen would be necessary? Does it keep the foam filter (see question #3) from entering the valve? When I searched for the OEM replacement gasket I found that the original P/N 865168 was superseded by 866326... The notable thing here is that the part description of the gasket also changed from "Gasket, Flame Arrestor" to just plain "Gasket". Did they remove the screen from it for the new part? 
  3. Once I removed the gasket I found a small foam filter (Mercruiser P/N 865266) in the bottom port of the intake air valve adapter body. Anyone know the function of this filter? Any air that is in the intake manifold has already passed through a much finer air filter so I don't understand it's purpose.

I ask all these questions because I'm trying to get the boat water ready in time for the 4th, and I'm struggling to find the OEM gasket readily available.

IAV Comparison Front.jpg

IAV Gasket Flame Arrestor.jpg

IAV Comparison Back.jpg

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scttmzr    2

The gasket included with the Standard Motor Products AC423 in case anyone searching in the future stumbles across this.

Standard Motor Products AC423.jpg

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Troy    234

Wow a detailed thread! great job. Sorry I can't help but I have the same engine and i'm following this thread for the future if I experience the same issues. 

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scttmzr    2

Well, I can report that the Standard Motor Products AC423 did NOT work. It only made the boat run worse. The OEM Mercruiser parts are on order now.

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nickj03b    0

I replaced mine last year due to idle issues.  I replaced it with the exact standard motors part you show and it cured my issues and boat has been running normal.  I have 2008 with the same motor.

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scttmzr    2
On 7/3/2018 at 0:42 PM, nickj03b said:

I replaced mine last year due to idle issues.  I replaced it with the exact standard motors part you show and it cured my issues and boat has been running normal.  I have 2008 with the same motor.

Hmmm, maybe I was just unlucky and received a defective part then.

I can now say with certainty that the issue was in fact the idle air valve. I installed the new OEM Mercruiser part last night, and it completely resolved the idle issue. Boat runs great now!

As a note for anyone else that goes to change their air idle valve, removing the air intake plenum (black cover with the scorpion logo on it) requires you to remove 2 nuts that are hidden beneath towards the rear of the engine. I had figured just the 6 torx bolts on top would do it, and it took me a while to find the other two nuts. They are a pain to get at!

Black Scorpion Air Intake Plenum Nuts.PNG

Edited by scttmzr
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Shane MT    2

My boat was running great and would start up cold with no effort, but I would occasionally have to give it some neutral throttle to start when warmed up. I read this and other threads and decided to change my IAC and IAC muffler. The muffler was black and solid where little air could go through, so I thought I had found the problem. Unfortunately, I still have the same situation where I have to give it some neutral throttle to start when warm. Regardless, I am glad I replaced these parts. The rotor, distributor cap, plugs, fuel filter, and cleaning fuel injectors are the next stop. 

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Shane MT    2
On 6/7/2020 at 8:55 AM, Aaron Johnson said:

Did you have to completely remove the spark arrester and throttlebody?  

You don't need to remove the throttle body. I think you can get away without removing the spark arrestor too.

 

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Astan115    0
On 4/28/2022 at 9:37 AM, Shane MT said:

My boat was running great and would start up cold with no effort, but I would occasionally have to give it some neutral throttle to start when warmed up. I read this and other threads and decided to change my IAC and IAC muffler. The muffler was black and solid where little air could go through, so I thought I had found the problem. Unfortunately, I still have the same situation where I have to give it some neutral throttle to start when warm. Regardless, I am glad I replaced these parts. The rotor, distributor cap, plugs, fuel filter, and cleaning fuel injectors are the next stop. 

Were you able to resolve the issue? Having the same problem with my 2005 centurion avalanche.

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jtryon    24
11 hours ago, Astan115 said:

Were you able to resolve the issue? Having the same problem with my 2005 centurion avalanche.

I just fixed the same issue on mine.  I’ve had to give mine gas at startup for two seasons and finally swapped it last month and it’s running perfectly with no gas needed at startup now.  Previously I would have to warm it up for 2-3 min on the trailer before launching so that it wouldn't stall when going into gear, now no issues.

If it helps, i found it cheapest at Nuwave Marine, SKU 710-8M0181068 and still a genuine Mercury part.  Don't try the Amazon/off-brand ones, many have tried and failed.  If you're looking elsewhere, the original part numbers are 862998 8M0181068.  When you go to replace it, the cover is harder than you think to get off.  There's 6 obvious bolts on the top of the engine cover, but then if you look towards the back of the motor where your pulleys are, there's two more nuts underneath the cover.  They're in line with the 3 top ones on each side which should help find them, maybe 3-4" in from the back edge of the cover.  If the cover doesn't come off easily like mine, take a pry bar or hammer and leverage the metal cooling jacket close to the back of the motor and gently pry up on the cover, it will pop right off.  I was standing on either side of the motor pulling with everything i had, tapping on the cover, pulling hard on one side at a time, and nothing would make it budge till i gently pried it up as stated.

once you get at the IAC valve, you should see what looks like a screened gasket which you'll want to keep.  buy an IAC muffler too, which is basically just little white foam squares that you stuff in the bottom port of the IAC intake, the top port stays clear.  clean off the old gasket material where it mounts to the engine, then the sequence is IAC muffler on bottom port, engine side>new gasket>screen>new IAC valve.  it should make sense once you're in there :)

good luck!

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Shane MT    2
On 6/13/2023 at 8:51 PM, Astan115 said:

Were you able to resolve the issue? Having the same problem with my 2005 centurion avalanche.

Mine still needs throttle when it’s warm sometimes even after replacing this. Starts right away cold though

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