Impeller / IAC

H

Her Diamond 2

Member
Jan 3, 2010
77
Midland, Ontario, Canada
Boat Info
2004 300 Sundancer
Engines
5.0L MPI - 260HP - Bravo 3
I recently had starboard engine trouble. My marina found two codes - high water temp and IAC (idle air control). I believe the high water temp code was an old code since my smart craft gauges showed proper water flow but since it was our first year with the boat, I decided to have the marina change both impellors. Our boat is a 2004 300 Sundancer with 5.0L and B3's. Does 7 hours labour seem a little high to change 2 impellors and the IAC? I was present when the IAC was changed and it took the mechanic 20 minutes (plus the 45 minutes it took him to drive back to the service dept to get a gasket he forgot - hence my concern since the service dept is only minutes from my boat).

Any opinions would be appreciated

Neil
 
Her Diamond 2 said:
I recently had starboard engine trouble. My marina found two codes - high water temp and IAC (idle air control). I believe the high water temp code was an old code since my smart craft gauges showed proper water flow but since it was our first year with the boat, I decided to have the marina change both impellors. Our boat is a 2004 300 Sundancer with 5.0L and B3's. Does 7 hours labour seem a little high to change 2 impellors and the IAC? I was present when the IAC was changed and it took the mechanic 20 minutes (plus the 45 minutes it took him to drive back to the service dept to get a gasket he forgot - hence my concern since the service dept is only minutes from my boat).

Any opinions would be appreciated

Neil
Click to expand...

I have not done my impellers yet (myself) but I know access is very good to the pump on the 300DA. I was told 3 hours labor for each engine on my boat but he said that was because they are so hard to get to on my 280 due to space and I believe them.

I would be willing to bet the "book" says 3 hours per and they charged you 30 min each on the IACs. I have changed several IACs and that should be a 5 minute deal each. The 45 minutes should be on him.

You can do the IACs on your own in the future. Very easy. I would not tackle the impellers unless to are mechanically inclined. Good news is you have plenty of space to work in.
 
The difficult part of changing the impellers is getting the hoses off the pump so you can remove it. Those hoes are really stiff and hard to reach.
 
What is the IAC (idle air control) and where is it located? Will it stop your engine from cranking? I have twil 350 Mercruisers and one won't crank now. Just looking for what may be my problem, It will turn over but seems to be either flooding, not firing or something else. Could this be a IAC?
 
Maybe a touch, just a touch on the high side but they may have travel time built in. A good mechanic should whip those out in 4 hours or less but there is set up and clean up to be factored.
 
flatrate on impellers is 2.5 hours each and 1.4 hours on iac. and Kscott, iac just controls idle. If you bumped the throttle up and it cranked but still didn't start like what you said in the other thread you started on your problem, the iac isn't the problem.
 
An IAC (idle air control) is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body.

Pay your mechanic about $300+ to do it for you or do it yourself and do a better job for about $100. It’s less than a one hour project the first time you do it and will leave you feeling you know your boat better.

The IAC controls the air flow at idle speed. A failed IAC causes the boat to not be able to idle.



Change your IAC, under $100, easy DIY job.

Also change the gasket.

As long as you are at it, get a new IAC muffler filter and lets make sure the Flame Arrester / Air Filter is clean.


Try www.boats.net or just shop around.

Pricing from Boats.net
803149 VALVE, IAC = $72.24
863112 Gasket = $ .91
863829 Muffler Iac = $ .92

$ is USA dollars



Parts you will need:
- IAC Vavle Idle Air Control, Mercury - Mercruiser 862998 1 $72.24
- Gasket, Mercury - Mercruiser 27-863112 1 $.91
- Muffler Iac (filter), Mercury - Mercruiser 35-863829 3 $.92
- Shipping ground = about $10.
- one spray can of carburetor cleaner, any brand. Wal-mart has this for about $2

Tools you will need:
- Open end wrenches, size #10 or #11 metric to remove and reinstall the flame arrester / air filter
- Allen wrench set to remove and reinstall the IAC
- Small needle nose pliers to remove the old IAC muffler filter.
- 2 gallon Bucket to wash the flame arrester
- boat wash or any liquid detergent to wash the flame arrester
- hose with running water to wash the flame arrester




The above costs are from boats.net I am not associated with them so feel free to shop around. The costs are only to give you one example so you know what to expect.


Remove your flame arrester part #24 / air filter. To do this remove engine cover knob #28, engine cover #27, (3) stainless nuts M6 #26, cover mount bracket #25 and then the flame arrestor / air filter #24

iac.jpg




Under the flame arrester and inside the air intake "THROTTLE BODY ASSEMBLY" part #1 is a mesh filter called a IAC muffler filter. It is shoved in a little rectangle. Pull this IAC muffler filter part #6 out then replace with new IAC muffler filter. It may look black and be hardily together if you have not changed it in a few years. You may need a small needle nose pliers to pull the old one out. Push the new one in by hand using your fingers.

On top of the engine is the IAC. It’s also under the area of your flame arrester / air filter but not inside then air intake. If this is your first time changing it, it will be painted back just like everything else. Your replacement part will most likely not be black, it will be shinny metal.


Unplug the wires at the IAC tip then remove 2 Allen wrench screws part #17, take off the old IAC part #16, make sure you have removed the gasket part #15, install the new IAC and gasket.


If you have not cleaned your flame arrester / air filter part #24 this year you may as well do this at the same time. Buy a can of carb cleaner, about $2 at Wal-mart and with the flame arrester / air filter part #24 removed and away from your boat spray the flame arrester / air filter part #24 with carb cleaner. Use the entire can turning the flame arrester / air filter as you spray it then rinse with water, wash in soapy water in the bucket, rinse again, shake it to get it mostly dry, let it dry the rest of the way in the sun, reinstall.



PS: I carry a spare IAC, gasket and IAC muffler / filter.
 
nice post presentation. I'll add newer engines have the iac on the side of the throttle body so you don't have to pull the flame arrestor. you still need same iac and gasket. There is a larger muffler you need and you hav to clean out the metal screen that you will see when you remove the iac.
 
kscott said:
What is the IAC (idle air control) and where is it located? Will it stop your engine from cranking? I have twil 350 Mercruisers and one won't crank now. Just looking for what may be my problem, It will turn over but seems to be either flooding, not firing or something else. Could this be a IAC?
Click to expand...

IAC will not keep your motor from cranking. It makes it nearly impossible at start idle.
 
Last edited:
I do not know about your engines but will add to this thread about what happened to mine. I have 8.1s in my boat and the engine alarm was working overtime. After many trips from the mechanic the problem turned out to be a bad temp sensor in the one of the exhaust manifolds. It was giving a 240 reading when the engine was really runnung at the correct temp. It did not always do it and the engine code did not say it was this sensor. This was a very expensive problem and ruined a whole summer of boat.
 
I had a IAC go bad a couple of months ago. Presentation is right on the money. I think it took me longer to get the IAC and the block it sits on aprat (from the factory paint) than it did to change the IAC. Everybody, and I mean everybody should be able to replace this on their own and save a few bucks.
 
Mine went bad while on a trip. Fortunately right at the end of the last day. We deflated the tubes but left them tied to the rear deck. I think they covered the exhaust vents on the rear of the boat causing the engine compartment to get hotter than normal thus contributing to the IAC failure.

If you decide to get an extra IAC for backup you want to have the gasket and an allen wrench to make the change.
 
I was curious, is the IAC the same as a GM car one or different? I don't have one but???????

Mike
 
I read enough about IAC failures that I went out and bought 2 right away. Mine haven't acted up yet, I think they're afraid of being replaced.
 
I am not sure about the IAC issue on my boat. My boat idles a little rough but not bad but she will stall out now and then. My issue is at 1000 RPM's and up. I just replaced both fuel filters but the port engine at those RPM's will move from say, 1200 RPM down to almost 400 RPMs and then quickly back up again. Some one said it might be the Analog Guage Interface or AGI. Any thoughts on that before I go and buy and AGI and the IAC? Or is it the IAC that is doing that.
 
You switch the IAC from the starboard to the port engine and see if that solves your problem.
 
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