Mercury 700sci problem
 

In keywest and trying to fix my 700sci. Engine will hardly run. Smartcraft reads boost valve error and ICA error. The engine is running rough and buzzer will not shut off. Anybody got suggestions. My boat is a 42 Fountain and has the name SLATER on the back. If anybody knows how to fix this my cell number is 901-335-1203. Thanks Andy Smith

Is the Mercury Racing truck not there?

Do you mean IAC error.........Idle Air Control valve? Not at all familiar with 700sci's and don't even know if they have IAC's??? Heard just yesterday about a 700sci supposedly having an IAC problem of some kind that caused a short in the engine wiring harness and melted some pins in the connector. Don't know what the symtoms where when it failed and don't want to send you on a wild goose chase, it's just a wierd problem that might be tough to find. If they do have IAC's and the valve is stuck partially open it could be a problem. If there is an IAC try unplugging the wire to it and see what happens. If there is an IAC it should be on or near the throttle body. If it does use an IAC and it gets unplugged it might be a hassle on starting and warm up and maybe also at big changes in engine load like when shifting in and out of gear?

Had a friend with 600sci burned up some wires and 2 computers and 2 iac valves
had to stop using deep cycle batteries

It does read IAC. I am still in keywest if anyone can offer help.

go find the NorTech trailer.. those guys will try and help you out.

Had the same problem twice what it is the computer will short out and tell the IAC valve to keep running until it burns up the plastic will actually melt out of the motor. I was told by one mechanic and mercury engineers it is the deep cycle batteries fountain installs. What I had to do was replace the ICA and computers and change the batteries. The batteries can only be starting not deep cycle or anything else.

Charge your batteries!

My batteries always had a good charge in them. It would happen at the end of the day during a poker run where the motors were running all day. My mechanic said he saw this problem with a lot of Fountains. I didn't learn about the batteries until I lost my second computer.

Can someone explain what the battery have to do with the IAC? I know the IAC is a elecrically powered mechanical part that is constantly moving while the engine runs and just figured they were prone to failure.

I had a IAC go bad on my old Eliminator and one on my 42 Fountain but never on my 38 Fountain. The eliminator had starting batteries, the 38 had a starting battery on one side and deep cells powering the other side. My 42 has the original betteries, but I am not sure what if they are starting or deep cell.

Sorry, but I have to call "BS!" on that one. Sounds more like Mercury grasping at straws to get off the hook. If it's true, then this is a great example of inept engineering.

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, are you confirming that it is true, a deep cell battery can kill the IAC, where a starting battery will not?

I read it as the IAC fails (shorted) causing the problem.

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.

This is a very surprising thread to follow.
These engines have an excellent reputation.
As does the engine package with the NXT Drive.


UD

i agree +1

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.

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

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?

IAC Solution
 

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.

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

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.

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.

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.

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.

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