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Mercury 700sci problem

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Old 12-21-2009, 02:37 PM
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Originally Posted by BKSAE View Post
What batteries did you change to, and have you had the problem since the battery change?
I was told just to use starting batteries. Only put about 3 hours on the new computers. With no problems so far.
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Old 12-21-2009, 05:54 PM
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Originally Posted by aTX427 View Post
Dustin, are you confirming that it is true, a deep cell battery can kill the IAC, where a starting battery will not?

Don't see how thats even remotely possible! But I was wrong once before ha ha

Last edited by Whipple Charged; 12-21-2009 at 06:06 PM.
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Old 12-21-2009, 05:57 PM
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Originally Posted by Raylar View Post
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?

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Ray @ Raylar
IAC or bypass shorts and then shorts the computer circuit its tied too. It does not blow the fuse its tied too. Battery could be a secondary issue, but I find it hard to believe.

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Old 12-21-2009, 06:04 PM
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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?
I've never seen a voltage spike up from deep cycle batteries, but I can say that I've maybe only data logged it 2-3 times and it would be impossible to test all scenario's, but I really don't see this is a high voltage spike. There is already a fuse tied to this circuit. I'm working on an extra circuit that plugs into the IAC and bypass valve connectors that has extra protection, high and low, so I'm working on that now.

I have a stack of PCM's here with the same issues, and some with other issues that we are repairing. The IAC repair is tough, but were getting it. We can repair all coil driver failures, which is also a common.
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Old 12-21-2009, 06:46 PM
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Dustin do you recommend to change the IAC after so many hours before it has a chance to fail? If so how many do you think?
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Old 12-22-2009, 01:24 PM
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Dustin do you recommend to change the IAC after so many hours before it has a chance to fail? If so how many do you think?
I really don't, we use the same IAC in the automotive field and it typically last well over 100,000 miles. I'm investigating it all, hope to have some good answers soon.
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Old 12-22-2009, 02:56 PM
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Originally Posted by Whipple Charged View Post
I really don't, we use the same IAC in the automotive field and it typically last well over 100,000 miles. I'm investigating it all, hope to have some good answers soon.
Thank you for all your quick responses. I will be looking forward to see if you come up with any solutions to the ICA and computer burning up. Once I change my drives to something stronger I will be ready for a upgrade on these motors.
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Old 12-27-2009, 10:02 AM
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Originally Posted by Whipple Charged View Post
I've never seen a voltage spike up from deep cycle batteries, but I can say that I've maybe only data logged it 2-3 times and it would be impossible to test all scenario's, but I really don't see this is a high voltage spike. There is already a fuse tied to this circuit. I'm working on an extra circuit that plugs into the IAC and bypass valve connectors that has extra protection, high and low, so I'm working on that now.

I have a stack of PCM's here with the same issues, and some with other issues that we are repairing. The IAC repair is tough, but were getting it. We can repair all coil driver failures, which is also a common.
Hey Dustin, please keep us posted on this issue, I know if anyone can come up with a good workaround on this it would be you!!
Mark
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