Air sucking sound/stall?

Today was our first day out this year. The boat ran great for a few hours. We stopped for a bit to let the kids swim and have a snack. When I started it back up, there was a strange air sucking sound that seemed to be coming from the air intake - kind of like something was trying to suck in air but was restricted, or something that normally sucks in air but is muffled had the muffler removed. Also, if it didn't stall right after cranking, it would stall after giving it a little throttle. I took off the plastic cover and the flame arrester and tried cranking it. It made the same sound and wouldn't run long enough for me to go back to the engine after cranking it to inspect better. With it off, I opened the throttle all the way to make sure the valve inside was opening properly. Then, soon afterward (maybe the next crank) the sound was gone and it ran fine. I put things back together, and we probably ran for another 45 minutes or so without any problems.

Any ideas what that sound could have been?

Thanks.

Vapor lock?

Bilge pump?

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Only guy I've heard of lately complaining of too much sucking.

It definitely was not the bilge pump.

I've never had a vapor lock problem before. The lake and air temps were around 75, which makes me think that wasn't the problem. Can vapor lock cause that kind of sound? It was loud enough to be quite noticable.

We took the boat out again yesterday and ran for 3-4 hours without any further problems.

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Originally Posted by WolfpackRider

It definitely was not the bilge pump.

I've never had a vapor lock problem before. The lake and air temps were around 75, which makes me think that wasn't the problem. Can vapor lock cause that kind of sound? It was loud enough to be quite noticable.

We took the boat out again yesterday and ran for 3-4 hours without any further problems.

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Maybe it was all the money being sucked out your wallet?

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Originally Posted by parrothd

Maybe it was all the money being sucked out your wallet?

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Hmm, now that's a possibility. :D It's a good thing it stopped!

We had the problem again today. I took a few videos. The first one was taken while the engine was running making the sound. I had the flame arrester off. So, it was a little louder, but not much. I had to have the throttle up quite a bit for it to run at all, though it only ran at an idle speed. A little into the video, the shot changes when I stepped back to lower the throttle at which point the sound got louder. Shortly after I stopped the video, it stalled.

http://www.youtube.com/watch?v=MEuQYYUvs4A

I also noticed that when I turned the key to the on position the fuel pump made a normal sound and then a louder sound right before it stopped. The second video is of the sound the fuel pump was making.

(2nd video posted in followup post because the forum is only letting me post one at a time)

After working with it for around an hour and letting it cool for that long, it finally ran normally again and did fine for the 7-8 minute ride back to the dock.

So, could that have just been vapor lock, or should I be looking at something else like a fuel pump going bad?

Thanks.

2nd video of fuel pump:

http://www.youtube.com/watch?v=G7cuYoquQOg

Might be bad gas from sitting up or the fuel filter has some trash in it. Could be why its a hit or miss on it.
Try putting some stabil in the gas before you go out next time.

mine had two injectors on the top of the intake and mine made a hissing noise when it bogged down..i noticed when it would go above 1500 rpms it would drop to one injector that was spraying fuel and when it would bogg it switched over to the other injector to spray fuel..if i were you i would replace your fuel filter and see what happends

I noticed that you have a V-drive. I think all of those suck to some degree.


In your second video, the pump has the louder sound at the end at the pressure has built up. While it's not normal that the pump would get louder, it is normal for the sound to change. Your pump may be wearing unusual to cause that sound. It may be about to break or it may last for 1000s of more hours.

Not sure about that sucking noise.

That my friend sounds like good old fashioned vapor lock. Well, it sounds like tye engine isnt getting fuel. Now whether thats vapor lock or not I dunno. Does this only happen when you have already been running the engine or will it happen on the first crank of the day?

Lol... Sounds like a bad pump or filter I'd be replacing both.. Better to be safe and not ruin a weekend or having to get towed..

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Sounds to me like the butterfly is not opening in the throttle body. Take a video with the camera pointing straight down into the throttle body. Or just try and open the butterfly valve. It sounds like it is starving for air. Similar to a carb choke getting stuck closed.

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That my friend sounds like good old fashioned vapor lock. Well, it sounds like tye engine isnt getting fuel. Now whether thats vapor lock or not I dunno. Does this only happen when you have already been running the engine or will it happen on the first crank of the day?

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I definitely agree that it is fuel related!

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Lol... Sounds like a bad pump or filter I'd be replacing both.. Better to be safe and not ruin a weekend or having to get towed..

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I'm going to start by replacing the fuel filter. I might go ahead and get a fuel pump to have ready.

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Sounds to me like the butterfly is not opening in the throttle body. Take a video with the camera pointing straight down into the throttle body. Or just try and open the butterfly valve. It sounds like it is starving for air. Similar to a carb choke getting stuck closed.

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The butterfly valve is opening when I move the throttle. Is it supposed to open some on its own at idle? If so, it definitely was not doing that.

Thanks for all the suggestions.

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Originally Posted by lewisb13

Does this only happen when you have already been running the engine or will it happen on the first crank of the day?

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Before you replace anything, I think you should answer this question....

I'm still in the vapor lock camp.

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Originally Posted by moombahighrider

Before you replace anything, I think you should answer this question....

I'm still in the vapor lock camp.

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Just watching his videos it totally reminds me of the vapor lock my 05 used to get. Since the engine is starved for fuel its trying to choke itself by closing the throttle plate and use the vacuum the engine is creating to suck more fuel in. I mean it textbook sounds the same its almost creapy.

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Originally Posted by lewisb13

Just watching his videos it totally reminds me of the vapor lock my 05 used to get. Since the engine is starved for fuel its trying to choke itself by closing the throttle plate and use the vacuum the engine is creating to suck more fuel in. I mean it textbook sounds the same its almost creapy.

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Plus, the conditions that are described are exactly the sort of thing that can produce vapor lock for me.

When you have a problem starting, push in the throttle only button on the control, throttle up 50% to 75% and see if it starts. The iac (idle air control) valve may be stuck and not allow enough or too much air into the motor for startup or idle. If you throttle up, it will take the iac circuit out of the equation.

I have a 2012 Mercury 383 Magnum with the same problem. I was just letting the engine warm up at the dock and it just started. I had the engine tuned up with new ignition parts. Runs perfect except that same loud sucking sound. It does it all the time cold or hot. Motor has 150 hours on it. throttle plate is opening and closing fine. I saw on a car forum a similar complaint and a suggestion was the "IAC is stuck open all the way" what does that mean and do marine engines have an IAC?

Thanks

Please let me know how you resolved this problem as I have the same boat and it has the same problem

It's kind of hard to say for sure since it was not a problem I could regularly repeat, but I think those that suggested vapor lock were right. If that was the problem, I think it must have been partly caused by ethanol in the gas because I had never had the problem before and the ambient air temperature was not as hot as what others had reported when having vapor lock. This year, I filled up with ethanol free gas when I winterized. I'll have a better idea about it in the spring when I get back out.

The problem only occurred for me after running the boat for a while and then having it sit off without the blower running. When starting again, it had the problem. I started running the blower while anchored until the air coming out had cooled somewhat and did not have the problem again. The only thing that has me unsure about vapor lock is why I never had a problem with it in the previous 6 years. The only answer I can come up with for that is that there might have been more ethanol in the gas than in previous years.

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Originally Posted by WolfpackRider

It's kind of hard to say for sure since it was not a problem I could regularly repeat, but I think those that suggested vapor lock were right. If that was the problem, I think it must have been partly caused by ethanol in the gas because I had never had the problem before and the ambient air temperature was not as hot as what others had reported when having vapor lock. This year, I filled up with ethanol free gas when I winterized. I'll have a better idea about it in the spring when I get back out.

The problem only occurred for me after running the boat for a while and then having it sit off without the blower running. When starting again, it had the problem. I started running the blower while anchored until the air coming out had cooled somewhat and did not have the problem again. The only thing that has me unsure about vapor lock is why I never had a problem with it in the previous 6 years. The only answer I can come up with for that is that there might have been more ethanol in the gas than in previous years.

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Our problem seems to be exactly the same, and we have the same boat and model. I had no problems for 5 years and last year it started doing this. If I through water over the hot fuel pump the problem goes away. If I run the blower or leave the hatch open I also do not have the problem. What concerns me is why now?? I never used to have to do this?? I have tried using different fuels but the problem continues.