IAC on 496 question...

[SEASTHEDAY]

Hey Team:

Anyone have any insight regarding issues with the IAC (Idle Air Controller) on a Mercruiser 496?

I've just repowered and the "whistling" is telling the mechanic that the IAC is bad. It’s under warranty... but …REALLY?.. a brand new engine with bad IAC? C’MON!!!

Is this a common thing for a 496???

Thx
Mark

 

[CAGE RATTLER]

It sounds like it is a common thing on the 8.1's but its not actually a bad IAC. Just a noisy one.

Heres a post you might be interested in.

http://www.offshoreonly.com/forums/general-q/104440-496-mag-whine-howl-whistle-noise.html

and another

http://boards.trailerboats.com/cgi-bin/trailerboats/ubb/ultimatebb.cgi?ubb=get_topic;f=6;t=001234


I did a little more checking on the IAC muffler (which is just a small piece of foam that silences the whistling).

Im not sure what serial number your engine is but i noticed when looking for parts that I could only find my model on the perfprotech.com site. Mercruiserparts.com doesnt even list my model according to the serial numbers.

perfprotech.com lists it as a 496 MAG EC (base model) & not the 496 Mag (base model). The base model shows an IAC muffler but the EC model doesnt. It will be listed under "Throttle Body, Mechanical Throttle-Shift " part number 5 (muffler IAC).

http://www.perfprotech.com/store/assembly/Throttle-Body-Mechanical-Throttle-Shift,11415-70.aspx

Remember, this listing is for the 496 base model and if your serial number begins with 1A******* then yours is also the 496 Mag EC Base model.

 

[Fun Times]

Hey Team:

Anyone have any insight regarding issues with the IAC (Idle Air Controller) on a Mercruiser 496?

I've just repowered and the "whistling" is telling the mechanic that the IAC is bad. It’s under warranty... but …REALLY?.. a brand new engine with bad IAC? C’MON!!!

Is this a common thing for a 496???

Thx
Mark

What year is your new engine to you?
If your not sure, Your welcome to post the engine serial number, I will be able to tell you the year if your in need of it also.

Do you hear the "whistling" sound while your holding a cruising speed of somewhere around the 3000 RPM range?

 

[CAGE RATTLER]

What year is your new engine to you?
If your not sure, Your welcome to post the engine serial number, I will be able to tell you the year if your in need of it also.

Do you hear the "whistling" sound while your holding a cruising speed of somewhere around the 3000 RPM range?

I can answer that for you. Hope you dont mind SEASTHEDAY.

he just bought the engine. Its a 2010 model and it was just put in. The boat hasnt been in the water yet. Im assumming they are hearing the whistling starting it on muffs.

In case your wondering, Im very interested in this as well cause i just bought the same exact engine but havent put it in yet.
By the way .... I edited some other info into my post above in case you missed it. Am I on the right track with the IAC muffler? Or could it still be a bad IAC?

 

[Fun Times]

If the engine is that new, And he has not even ran the boat on the water yet at cruising speeds, then more then likely it should not be the whistling sound effect that I had in mind that I was going to suggest checking for.
The IAC muffler is worth trying, It helps a lot with the idling sounds.

I can answer that for you. Hope you dont mind SEASTHEDAY.

he just bought the engine. Its a 2010 model and it was just put in. The boat hasnt been in the water yet. Im assumming they are hearing the whistling starting it on muffs.

In case your wondering, Im very interested in this as well cause i just bought the same exact engine but havent put it in yet.
By the way .... I edited some other info into my post above in case you missed it. Am I on the right track with the IAC muffler? Or could it still be a bad IAC?

 

[Jimmy Buoy]

Both my engines whistle as described. No mufflers are present and they are not the "Mag" engines (Base Engine 370Hp).

I've chosen not to add the mufflers and have just become familiar with the whistle. As the 3rd owner, I'm not sure if the engines originally had mufflers or not - but they don't seem to need them to run well.:thumbsup:

 

[Presentation]

Missing IAC muffler = whistling noise. Technically this does no engine damage, just causes a whistling noise.

The IAC muffler is nothing more than a piece of mesh foam. It has no frame.


The only reason that mesh piece of foam is not called a filter is the air is already filtered by the flame arrester so it’s not filtering; it’s muffling that whistling noise.

 

[SEASTHEDAY]

Hey guys… sorry….. I’ve been working like a dawg… and have had little time to nudge the mechanic and/or even got out on the water….

Hmm… IAC muffler…. Eric hasn’t mentioned that at all.. I’ll have to ask…that is interesting it hasn’t come up as of yet… as I recall…. the mention at the time was if it was the IAC then the engine is running lean and we don’t want that….and we should hold of with anything else until he could talk directly with Mercruiser.

We had put the boat in the water for a sea trail…. And even ran it a bit still sorta in the sling just in case.. After a little while, we took it out to buzz around. That is when we hit the 2 beeps every minute… brought it back to the dock… hooked up the computer.. figured out the oil pressure sensor was installed wrong… fixed that .. went back out.. then heard the whistle…brought it back to the slip… and waited… then waited some more.. and then …yes… a bit more…

The engine was finally fixed on 7/1. Just in time for the 4th… Eric, my mechanic, and the shop where I bought the engine from, had to do the paper work with the warranty, and did …whatever else they needed to do… to get to the point where they could log a problem ticket with a tech who works at Mercruiser and start troubleshooting the issue with them. (…that only took 2 weeks… I’m not bitter….) they gave Eric a few things to look at. One of the things was a plate which the IAC is connected to. This plate was suppose to be perfectly flat, but was off by 2,000 (of an inch perhaps…didn’t really follow) Eric had a machine shop he knows flatten it to within specs, got 2 new gaskets and hooked everything back up. It works like a champ now. So far no issues… Still do not have a sense as to root cause… or what might have happened to that plate. Going forward, I’ll try to focus on ….how to prepare for the next issue or concern regarding the IAC……

We took it out over the 4th of July weekend… went to Napatree Point (Watch Hill Rhode Island) for a couple of days… (And yes worked called me while I was there…) The engine is running great. It’s so quite compared to the 454; I’m not yelling at my guests while at cruising speed. I’ve been babying it… not going too crazy…it’s still in the break in period…. I did get up to 4200 RPM … and hit like 32 knots or so.. then brought it back down to about 3200 RPM.. 22 knots… I’m hearing that “guardian” will kick in if I get close to 5000 RPM which I guess is red line. Won’t be pushing it that hard any time soon….

 

[zboaterctf]

It sounds like it is a common thing on the 8.1's but its not actually a bad IAC. Just a noisy one.

Heres a post you might be interested in.

http://www.offshoreonly.com/forums/general-q/104440-496-mag-whine-howl-whistle-noise.html

Remember, this listing is for the 496 base model and if your serial number begins with 1A******* then yours is also the 496 Mag EC Base model.

Thanks - I have had the boat in multiple times for this annoying sound and will now look to see if this fixes it. I have the 496 MAG on my 290 (2008) and also get this "whine" right around 3K ...

 

[CAGE RATTLER]

I have about 12 hours now on my 496 MAG and have yet to hear any noticable whistle or whine. Might just be because i have to run over 3500 RPM's to stay on plane though.