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  #21  
Old 05-01-2014, 08:06 PM
willg willg is offline
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Quote:
Originally Posted by 1redTA View Post
sounds like a dirty IAC valve
Yeah. I had this go bad on my MC and on a boat with a 454 Mercruiser motor. My MC LTR engine also had the throttle position sensor go bad and the boat would idle at 1000 rpm all the time. The valve is like $15 from the auto parts store. I don't know if a drive by wire boat has a tps sensor, but my money is something related to the intake air control or possibly the throttle body malfunctioning.

The symptoms on both were surging and stalling, cold or warm.

You can usually check the sensors, but they are so cheap its just worth replacing for piece of mind.

If you can figure out a gm car with the same motor, you can usually use it to cross reference parts at Napa/advance.

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  #22  
Old 05-01-2014, 08:21 PM
willg willg is offline
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This might be an interesting read, I know its an older boat, but he fixed his idle problem with a throttle position sensor

http://www.supraboats.com/bbs/showth...metimes-04-SSV

For what its worth, here's the IAC from bakes online ($220):
http://www.bakesonline.com/detail.aspx?ID=2410

and here is what I'm willing to bet is the same part from Summit ($70, they also have a cheaper one):
http://www.summitracing.com/parts/smp-ac147/overview/


And here is the MAP sensor
Bakes ($95):
http://www.bakesonline.com/detail.aspx?ID=1342

Summit ($50):
http://www.summitracing.com/parts/sm...make/chevrolet


I would think it was one of those. If you are at a dead end, it might be worth buying the cheapest one from summit and just changing them just to be sure. There are diagnostic methods for testing these components, but you are probably going to have to pay an hours labor to test them, its like a 2 minute job to just swap them.

Last edited by willg; 05-01-2014 at 08:31 PM. Reason: moar info
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  #23  
Old 05-03-2014, 03:50 PM
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No need to use the "toss parts at it method of diagnosis". There are tests for each of those parts.
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  #24  
Old 05-03-2014, 04:27 PM
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Originally Posted by sraab928 View Post
Good Morning all - I am in the process of purchasing (under contract) a 2008 Mastercraft CSX 220 SS with an Indmar LY6 400hp engine. My question is this - when you first start the engine cold (not when its warm) the rpms go up and down (not sure of the range but its quite noticeable) for the first 15-30 seconds or so. I am told its the fly by wire controls setting themselves up. Since I have never owned a boat with this type of control I am curious if this statement is accurate. I searched the forum and couldnt find anything. I also looked over the Indmar manual on line and found nothing about it either.

I just want to make sure this is true before taking delivery.

Thank you in advance
Scott
Shoot a video of it after sitting overnight, then e-mail it to MC and ask for their opinion.
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  #25  
Old 08-19-2014, 01:32 AM
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Hunting

Mine does the same.
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  #26  
Old 08-19-2014, 06:46 AM
XSTARSHREDDER XSTARSHREDDER is offline
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Boat: 2008 XSTAR LY6 W/ FLY HIGH SYSTEM, ACME PROPELLER UPGRADE
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Same here. My LY6 does the exact thing and I was wondering about it. Thanks for the input!
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  #27  
Old 08-20-2014, 09:25 AM
pgw pgw is offline
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My 2008 LY6 has always done it. Seems to be worst when started after a long break 2 - 3 months and sometimes stalls. If the boat is being used daily it doesn't do it. If it sits for a week it will hunt for 10 - 20 seconds.


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  #28  
Old 08-22-2014, 03:29 PM
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The LY6 RPM "Hunting" issue when cold was due to the fact that this was the first engine with variable valve timing. The surging was due to the amount of time that it took for oil to travel through the engine, through the hollow section of the camshaft and into the cam phaser which is essentially a rotary hydraulic cylinder. The surging was normal on those engines and was more of an issue in marine than automotive because of the heavier oil that we use. There was a cam phaser change and later models do not exhibit this surging.
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  #29  
Old 08-22-2014, 10:07 PM
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Quote:
Originally Posted by Engine Nut View Post
The LY6 RPM "Hunting" issue when cold was due to the fact that this was the first engine with variable valve timing. The surging was due to the amount of time that it took for oil to travel through the engine, through the hollow section of the camshaft and into the cam phaser which is essentially a rotary hydraulic cylinder. The surging was normal on those engines and was more of an issue in marine than automotive because of the heavier oil that we use. There was a cam phaser change and later models do not exhibit this surging.
Always enjoy the input from Enginenut!
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  #30  
Old 11-03-2014, 07:39 PM
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gambier gambier is offline
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Boat: X-35, 2008, LY6 Closed Cooled
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+1 for my LY6 hunting when cold. Was no big deal until the last month or so where it would sometimes quit while hunting. Progressively got worse, would quite 2 or 3 times before running properly. After that, ran fine all day/weekend.

Now it consistently quits at cold startup. End of season so want to get this worked on over the winter.

I noticed a few others that experienced quitting at cold start, anyone solve this? Any suggestions from others to look for?

thanks

scott
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