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Stuart Adair

Possible air intake valve ?

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Hi,

Went out up the river on Sunday for about an hour. Moored up outside a pub for a couple of pints and then headed for home. We were doing about 6mph @ 1100 rpm when the engine just cut out. No warning just as if I'd turned off the key. Put it into neutral, turned the key and she fired straight back up. About 1/2 hr further up the river exactly the same thing happened. Started up again and she ran without incident back to the boatyard.

Yesterday I had her on tickover in the boatyard and went over every wire I could find, wiggling and pulling to make sure nothing was loose on both the engine and under the dashboard but I couldn't replicate the issue.

I've done a bit of research and the suggestion might be the air intake valve. What do you think ?

Thanks

Stu

 

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That's exactly what's it's going to be.  Usually though, the boat will idle but as soon as you put it into gear it will stall out.  But my boat was doing almost the same as yours and as soon as I replaced the Idle Control Valve, she had no issues.  Very easy and cheap fix too, this is definitely a do it yourself job. 

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You didn't mention what engine you have. But it does sound like what mine would do but keep running. Easy fix thou.

 

.

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I have twin mercs and my Port side ICV went out on me right before I was going to try to back her into the slip.  Mind you now that my slip has super strong currents and the wind conditions were not in my favor that day.  It figures the engine I needed to get her the rest of the way into the slip was the one that kept stalling when I put it in gear.  I was not able to back her in and a guy on a Skiff came over and helped pull us into the slip.  Not fun after being on the water in the hot sun all day.

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5 hours ago, Stuart Adair said:

Hi,

 We were doing about 6mph @ 1100 rpm when the engine just cut out. No warning just as if I'd turned off the key. Put it into neutral, turned the key and she fired straight back up. About 1/2 hr further up the river exactly the same thing happened. Started up again and she ran without incident back to the boatyard.

I had this exact issue a couple years ago with a brand new IAC installed.  Never found the cause.  We had trailered the boat to Florida and upon launch, it died between launching and tying up at the dock.  Then while idling on the ICW, it died again.  Just as you described...as if somebody turned the key off.  It started right back up and then a half hour later did the same thing.  Did it a few times that day and the next.  Had a local mechanic go over every wire, connection, etc. and couldn't find an issue.  Following day, we took the boat to the Bahamas and have never had it happen again.

One speculation was that there was somehow some air in the lines, fuel filter, etc.  Another thought was vapor lock, but I don't think it would have started back up immediately.  But the ultimate guess is that something just came loose, and after all the fiddling, we must have corrected the loose connection.  Don't throw too much money at it too soon.

By the way, the IACs crap out at about 300 hours on Mercruiser motors.  So if you're near 300 hours, and if you have a Mercruiser, definitely replace it.

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Thank you for your replies. I've got a Merc 5.7 with 810 hrs on so I'll change the valve as advised and let's see what happens.  Stu 

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All,

I've had a result today so thought I'd share what the problem is with you. I ordered a new water/fuel separator filter as a precaution and went down to photograph the IAC Valve to compare with those for sale online. We had the boat ticking over as usual with no issues, until I span left in my seat and the boat turned off. I realised that I'd just slightly nudged the key with my knee. I did some further tests and with the engine running, just turning the key slightly to the left by a few mm turns off the engine. So it sounds like  I need to get myself a new ignition key barrel. Happy result and problem solved for less than £20.

 

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On 4/7/2019 at 10:33 AM, Stuart Adair said:

All,

I've had a result today so thought I'd share what the problem is with you. I ordered a new water/fuel separator filter as a precaution and went down to photograph the IAC Valve to compare with those for sale online. We had the boat ticking over as usual with no issues, until I span left in my seat and the boat turned off. I realised that I'd just slightly nudged the key with my knee. I did some further tests and with the engine running, just turning the key slightly to the left by a few mm turns off the engine. So it sounds like  I need to get myself a new ignition key barrel. Happy result and problem solved for less than £20.

 

That's good news!  I don't recall which 5.7 you have, but if it's a newer 350 Mag MPI, be careful with the spin-on fuel/water separator.  If it's the same as mine, the cool fuel module houses the filter.  I was advised by a marine mechanic to add a spin-on type of fuel/water separator in-line between the fuel tank and the cool fuel module.  After some research (and before installing it) I read that Mercury cautions against adding the spin-on separator with this engine because of the very strict tolerances (I presume pressure tolerances) and that it may create other issues with the engine. 

So, if you're talking about the cool fuel module filter...then by all means replace that regularly.  If adding a spin-on style, you might want to talk to Mercury.

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Sounds very similar to my issue! I'm scratching my head about this.

2011 5.0 mpi merc with bravo 3

The boat has stalled out 3 times on me. The last two times happening on Saturday and Sunday. 122 hours on the engine. When I'm at idle speeds for a period of time (about 5-10 min) the boat refuses to take throttle when exiting the no wake zone and eventually dies out. After sitting for about 20 min....she fires right back up. The boat has ran great for us before and after these mishaps. Does this sound like a similar problem? Just trying to figure out where to start! I'll monitor this site or you can shoot me a direct email with any suggestions. I appreciate it! It's driving me crazy!

ppuriefoy@outlook.com

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The IAC valves ( Idle Air Control) will fail in two fashions. If the servo motor dies that is an electrical fault that the ECM will see, and set an "Engine Sensor" alarm. If they die mechanically, basically getting stuck in the wrong position now and then, drive-ability goes to heck, but the ECM stays happy. Some have said that they remove the IAC and clean the pindel, but I have never tried that as aftermarket replacements are not all that expensive, and it's a 5 minute change-out.  W

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PPuriefoy, definitely sounds like the IAC valve.  Wingnut is right, it's better to buy a new one.  I did clean up and older one and I keep it on the boat in case of an emergency on the water though. 

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I’m going to replace the IAC. I think it’s getting stuck because I’m not getting an alarm. Is it just coincidence that after it sits for 15-20 min it starts back up and runs like nothing ever happened? Also, why the heck does it happen after spending time at idle speed? I’m thinking about replacing the fuel filter also. After it won’t take throttle and I turn it off....the boat won’t start. I can hear the fuel pump turn on, and the boat turns over but it won’t start. It’s like it’s not getting fuel!

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