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Mercury 700sci problem

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Old 12-19-2009, 01:54 PM
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Computer has failed, it has a bad circuit, which is shared between the IAC and boost control valve. I'm working on a fix for it right now, but its not easy, but hope to have an option in the next few weeks. This is a VERY common problem. Typically its the IAC valve that shorts the circuit. I've seen many try the "good" computer from a 2nd motor and it instantly kills it as well, so be careful.
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Old 12-20-2009, 12:47 PM
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Dustin, are you confirming that it is true, a deep cell battery can kill the IAC, where a starting battery will not?
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Old 12-20-2009, 01:36 PM
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I read it as the IAC fails (shorted) causing the problem.
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Old 12-20-2009, 04:07 PM
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I can't see how a deep cycle battery would have anything to do with it. Even if the deep cycle was not fully charged, components must be designed not to burn up.
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Old 12-20-2009, 04:31 PM
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This is a very surprising thread to follow.
These engines have an excellent reputation.
As does the engine package with the NXT Drive.


UD
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Old 12-20-2009, 08:08 PM
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Quote:
Originally Posted by Wildman_grafix View Post
I read it as the IAC fails (shorted) causing the problem.
i agree +1
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Old 12-20-2009, 09:22 PM
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Quote:
Originally Posted by Uncle Dave View Post
This is a very surprising thread to follow.
These engines have an excellent reputation.
As does the engine package with the NXT Drive.


UD
It is not isolated to 700's. 500efi's, 525efi's, 600sci and 700sci's all run the same part number and they all burn out. I had one go out in a 2000 model 500efi at 120hrs and another on my 700sci with 80hrs. Now I keep two spares with me at all times. The IAC is mechanical and always moving. I just figured they were prone to failure.
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Old 12-20-2009, 11:44 PM
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If I read Dustins post correctly, he is not apparently saying the battery is causing the problem, I believe he is saying its a computer problem, shorting out a ECM circut that is being caused by an IAC overload or something.
Mercury uses a Ford type IAC motor and I know these are sometimes proned to burn up from the high amperage load they can create when they start going bad.
Sounds like something Mercury has seen before, I am surprised they don't have a technical service bulletin or something out about a fix or something?

Best Regards,
Ray @ Raylar
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Old 12-21-2009, 08:26 AM
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Quote:
Originally Posted by Whipple Charged View Post
Computer has failed, it has a bad circuit, which is shared between the IAC and boost control valve. I'm working on a fix for it right now, but its not easy, but hope to have an option in the next few weeks. This is a VERY common problem. Typically its the IAC valve that shorts the circuit. I've seen many try the "good" computer from a 2nd motor and it instantly kills it as well, so be careful.
Dustin,
I was the one who lost 2 computers with the ICA valves in one month. If it is the valve taking out the computer can a inline fuse be installed between the to for protection of the computer? The first question from second mechanic that looked at my boat was do you have deep cycle batteries. He called mercury to try to get it warranty and that was the same question they asked. I don't understand it either but they say the batteries have a memory and produce high voltage spikes. So that is why I changed the batteries plus they were getting old.
Bob

PS: Are you working on a fix for the bad computers or only to try to stop burning them up?

Last edited by mudslide; 12-21-2009 at 09:22 AM.
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Old 12-21-2009, 02:18 PM
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Default IAC Solution

What batteries did you change to, and have you had the problem since the battery change?
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