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interference coming from 115 etec

Old 02-25-2015, 03:15 AM
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Default interference coming from 115 etec

i have 07 115 etec and furuno 587 with tm260 im getting bad interference on 50khz side tryed local dealership he wasn't really sure heres few photos of my on drift with tranducer cable on deck and sounder running on battery pack
Old 02-26-2015, 08:21 AM
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First of all, I want to commend you for the thorough method you have used in testing, that is, the isolation of the power for the echo sounder to its own battery and the isolation of the cable to be separate from other electrical cables. Both could be sources for interference to enter the echo sounder. Next, I want to commend you for the very nice screen display showing the three levels of interference.

I am afraid I cannot offer any solution, but I can offer a few comments. It appears that the interference is likely to be from the spark ignition voltage of the E-TEC. It seems like the coupling of this interference must be coming into the echo sounder via the transducer itself, as that is the only means that remained in your test; you eliminated conduction of the interference via the power and via the cables. Other than moving the transducer farther away from the E-TEC, I don't see a remedy to get rid of the interference. We must look at reducing the strength of the interference at its source.

In the E-TEC there are two epochs for spark ignition. Prior to model year 2009, the E-TEC engines used a capacitive discharge system to generate the voltage for spark ignition. In 2009 the E-TEC changed to an inductive discharge for spark ignition voltage generation. This suggests your model-year 2007 E-TEC has the capacitor discharge ignition.

I believe that the capacitor discharge ignitions tend to generate a higher voltage, shorter duration spark. Such a signal may be more likely to generate interference than the inductive discharge spark ignition, when tends to produce a longer duration spark but at a lower voltage. I also think the capacitive discharge might fire a plug multiple times, creating perhaps more interference.

In the E-TEC engines it is now common that all the high-voltage spark ignition wires are encased in a plastic and flexible, but still somewhat conductive sheath, and a copper drain wire is run in that sheath to further help contain the spark voltage. I don't have first-hand knowledge of how your particular c.2007 engine was built. I think it has those conductive sheaths and drain wires, but I am not certain. I suggest you look closely at the spark wiring to verify it has the conductive sheaths covering it and the drain wires are intact and connected.

I do not think there is any way to convert a capacitor discharge ignition E-TEC into an inductive discharge ignition, so you are stuck with the capacitor discharge ignition. Give the spark wires a close inspection. Perhaps something is awry with them.

There is also the possibility that one of the spark plugs is not firing, and the result is the spark voltage is leaking to ground by some other path. This could also help radiate the interference. There is also a possibility that the installed plugs are not of the proper radio-frequency-interference suppressing design. It might be prudent to check the spark plugs against the recommended type to be certain they are correct.

Last edited by jhebert; 02-26-2015 at 11:05 AM.
Old 02-27-2015, 05:03 PM
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Originally Posted by jhebert View Post
First of all, I want to commend you for the thorough method you have used in testing, that is, the isolation of the power for the echo sounder to its own battery and the isolation of the cable to be separate from other electrical cables. Both could be sources for interference to enter the echo sounder. Next, I want to commend you for the very nice screen display showing the three levels of interference.

I am afraid I cannot offer any solution, but I can offer a few comments. It appears that the interference is likely to be from the spark ignition voltage of the E-TEC. It seems like the coupling of this interference must be coming into the echo sounder via the transducer itself, as that is the only means that remained in your test; you eliminated conduction of the interference via the power and via the cables. Other than moving the transducer farther away from the E-TEC, I don't see a remedy to get rid of the interference. We must look at reducing the strength of the interference at its source.

In the E-TEC there are two epochs for spark ignition. Prior to model year 2009, the E-TEC engines used a capacitive discharge system to generate the voltage for spark ignition. In 2009 the E-TEC changed to an inductive discharge for spark ignition voltage generation. This suggests your model-year 2007 E-TEC has the capacitor discharge ignition.

I believe that the capacitor discharge ignitions tend to generate a higher voltage, shorter duration spark. Such a signal may be more likely to generate interference than the inductive discharge spark ignition, when tends to produce a longer duration spark but at a lower voltage. I also think the capacitive discharge might fire a plug multiple times, creating perhaps more interference.

In the E-TEC engines it is now common that all the high-voltage spark ignition wires are encased in a plastic and flexible, but still somewhat conductive sheath, and a copper drain wire is run in that sheath to further help contain the spark voltage. I don't have first-hand knowledge of how your particular c.2007 engine was built. I think it has those conductive sheaths and drain wires, but I am not certain. I suggest you look closely at the spark wiring to verify it has the conductive sheaths covering it and the drain wires are intact and connected.

I do not think there is any way to convert a capacitor discharge ignition E-TEC into an inductive discharge ignition, so you are stuck with the capacitor discharge ignition. Give the spark wires a close inspection. Perhaps something is awry with them.

There is also the possibility that one of the spark plugs is not firing, and the result is the spark voltage is leaking to ground by some other path. This could also help radiate the interference. There is also a possibility that the installed plugs are not of the proper radio-frequency-interference suppressing design. It might be prudent to check the spark plugs against the recommended type to be certain they are correct.
thanks for the infomation il have a look some time to day im pretty sure spark plug leads do have ground wires running of them and the spark plug have just been change at service 30hrs ago although there not whats written on serial plate ive been told there the correct ones and just a updated model
Old 02-27-2015, 06:57 PM
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Is this something new or had this always been a problem? I assume this doesn't happen at 200 Hz?
Old 02-27-2015, 10:56 PM
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Originally Posted by mahimahi99 View Post
Is this something new or had this always been a problem? I assume this doesn't happen at 200 Hz?
its always been a problem and it only affexs 50khz side
all the spark plug leads are intact one how ever when u push it on its clicks but them the seal rubber slides back about 20mm not sure if its loosing contact or not gonna play around with it a bit more
Old 02-28-2015, 06:26 AM
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Originally Posted by junior88 View Post
...spark plug leads...not sure if...loosing contact or not...
A gap between the spark plug wire and the cap of the spark plug could be the cause of excessive radio frequency interference. Typically the spark is strong enough to jump two gaps, one in the wire lead and the intended gap at the plug electrode, so the engine may be running more or less normally, but you would be generating more interference than normal from the exposed arcing in the wire lead.

The E-TEC is a modern outboard engine and depends on a high-speed real-time computer controller. For that reason the spark ignition system is designed to not generate much radio frequency interference, as such interference would be likely to cause problems for the engine's own computer control system.

It is possible with a SONAR to see some spark interference from an E-TEC, particularly when the SONAR gain increases for deep water echo sounding. It has been my experience that by keeping the cable for the transducer physically isolated from all the other boat rigging cables and engine cables that any interference can be minimized.
Old 02-28-2015, 05:06 PM
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Originally Posted by jhebert View Post
A gap between the spark plug wire and the cap of the spark plug could be the cause of excessive radio frequency interference. Typically the spark is strong enough to jump two gaps, one in the wire lead and the intended gap at the plug electrode, so the engine may be running more or less normally, but you would be generating more interference than normal from the exposed arcing in the wire lead.

The E-TEC is a modern outboard engine and depends on a high-speed real-time computer controller. For that reason the spark ignition system is designed to not generate much radio frequency interference, as such interference would be likely to cause problems for the engine's own computer control system.

It is possible with a SONAR to see some spark interference from an E-TEC, particularly when the SONAR gain increases for deep water echo sounding. It has been my experience that by keeping the cable for the transducer physically isolated from all the other boat rigging cables and engine cables that any interference can be minimized.
ok thank il see what i can work out over nexr few weeks

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