Could I "Faraday Ring" an outboard ?

LONG_KEELER

LONG_KEELER

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I have an outboard in a well. Great for many reasons but lousy for electrical interference.

I seem to be suffering from " Electro Magnetic Interference" because the outboard is too near electrical instruments.

Could I line the inside of the engine cover with something along the lines of the "Faraday Ring" ?

Has anyone tried this ? Might it work ?

Thanks in advance .
 
LONG_KEELER said:
I have an outboard in a well. Great for many reasons but lousy for electrical interference.

I seem to be suffering from " Electro Magnetic Interference" because the outboard is too near electrical instruments.

Could I line the inside of the engine cover with something along the lines of the "Faraday Ring" ?

Has anyone tried this ? Might it work ?

Thanks in advance .
Click to expand...

Well, in theory lining the cover with foil or fine metal gauze would help - but it wouldn't work very well because you can't completely enclose the engine, and RF interference will diffract through any hole such as you need for the air intake, exhaust and drive shaft. It's a Faraday Cage you want, but I doubt it would be terribly effective.

The problem is that an ignition circuit is certain to generate SOME interference; it's a matter of how best to mitigate it. The ignition should have RF suppression devices fitted - are these all in good condition? Look for capacitors and ferrite cores. Capacitors are a likely culprit - they don't last forever, especially in the environment of a marine engine. If there's a charging system, is there a commutator that needs worn/dirty brushes changing?

Otherwise, distance is your friend, and moving signal wire runs away from the well and/or moving sensitive equipment such as compass sensors is probably all you can do. It needn't be far - doubling the distance reduces the interference 4 times.
 
LONG_KEELER said:
I have an outboard in a well. Great for many reasons but lousy for electrical interference.

I seem to be suffering from " Electro Magnetic Interference" because the outboard is too near electrical instruments.

Could I line the inside of the engine cover with something along the lines of the "Faraday Ring" ?

Has anyone tried this ? Might it work ?

Thanks in advance .
Click to expand...

AntarcticPilot said:
Well, in theory lining the cover with foil or fine metal gauze would help - but it wouldn't work very well because you can't completely enclose the engine, and RF interference will diffract through any hole such as you need for the air intake, exhaust and drive shaft. It's a Faraday Cage you want, but I doubt it would be terribly effective.

The problem is that an ignition circuit is certain to generate SOME interference; it's a matter of how best to mitigate it. The ignition should have RF suppression devices fitted - are these all in good condition? Look for capacitors and ferrite cores. Capacitors are a likely culprit - they don't last forever, especially in the environment of a marine engine. If there's a charging system, is there a commutator that needs worn/dirty brushes changing?

Otherwise, distance is your friend, and moving signal wire runs away from the well and/or moving sensitive equipment such as compass sensors is probably all you can do. It needn't be far - doubling the distance reduces the interference 4 times.
Click to expand...

I've not come across capacitors or ferrite cores to suppress radio interference in small outboards and charging systems usually consist of a stator coil and a rectifier and possibly a solid state regulator, no commutator or brushes.

It might be worth checking that suppressed spark plugs are fitted. They will be inductively suppressed Champion "Q" series plugs in the case of most Johnson or Evinrude engines or resistor suppressed plugs such as NGK plugs with an "R" in the number in the case of most other popular brands.
What engine do you have and what sparkplugs are fitted ?
 
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Many thanks to A. Pilot and Vic for responding.

The Spark Plug is - NGKDCPR6E,

Engine Nos are - OR305029, May 2009, MA4M 4ST .

The main problem is the Raymarine 1000+ Tiller Pilot. It is very close to the outboard . As mentioned, at an arm's length
further away, there is no interference at all.

Wrapping the autopilot in metal foil produced no difference.

When I was down at the yard, I had a very quick word with a marine electrician. He had to charge off but mentioned a Ferrite Bead/Core .
A search reveals that these slip over a power cable but I would have thought that the magnetic force from the engine would not be affected.

Interestingly, the magnetic interference took some time to subside even after turning the engine off.
 
LONG_KEELER said:
Many thanks to A. Pilot and Vic for responding.

The Spark Plug is - NGKDCPR6E,

Engine Nos are - OR305029, May 2009, MA4M 4ST .

The main problem is the Raymarine 1000+ Tiller Pilot. It is very close to the outboard . As mentioned, at an arm's length
further away, there is no interference at all.

Wrapping the autopilot in metal foil produced no difference.

When I was down at the yard, I had a very quick word with a marine electrician. He had to charge off but mentioned a Ferrite Bead/Core .
A search reveals that these slip over a power cable but I would have thought that the magnetic force from the engine would not be affected.

Interestingly, the magnetic interference took some time to subside even after turning the engine off.
Click to expand...

If it's magnetic interference, you can't shield it, and there isn't much you can do about it. Electro-magnetic interference caused by the ignition circuit and/or plugs you might stand a chance, but if it is truly magnetic fields from the motor interfering with the built in compass, the only solution is to use an external compass mounted elsewhere in the boat. Some people have mentioned dismantling the compass out of the ST1000 and putting it elsewhere, but of course, that's a more risky operation!
 
LONG_KEELER said:
The main problem is the Raymarine 1000+ Tiller Pilot. It is very close to the outboard . As mentioned, at an arm's length
further away, there is no interference at all.
Click to expand...

Sorry I failed to realised you were talking about the magnetic effect.


As Antarctic Pilot says you cannot shield it.

There are some powerful magnets in the flywheel of your outboard and some coils which become magnetised when the engine is running. Distance between it and the auto pilot compass is I think the only solution.
 
The autopilot relies on the earth's magnetic field.
If you are smothering that with a varying magnetic field from the running outboard, as well as distorting it by having the iron content of the outboard in the field, it seems likely not to work.

However if the issue is the wiring of the pilot picking up induced noise, you could try:
1) twisting the + and - feed to the pilot together
2) adding a ferrite around them close to the pilot.
You might find a suitable ferrite on the lead of an old piece of IT equipment, such as the video lead of an old monitor.
3) add a capacitor or two across the + and - supply close to the pilot, something like 100nF and a few uF might be good values to try.
The 100nF (nano farads) should help at radio frequencies, the larger one might help with lower frequencies, such as the AC produced by the outboards charging coils.

As an experiment, you might try powering the pilot with a separate battery on short twisted leads?

The idea of twisting the leads is partly to minimise the loop area, and partly to make any induction cancel out by reversing with every twist.
If the rest of your wiring has the gnd/rtn/-ve a long way from the + supply wires, that is something else you can work on.

You could get a cheap hikers compass and see how close it can be to the outboard before it goes potty. You may alter its magnetism, so use a cheap one!
 
Magnetic interference can be reduced by an iron sheet between the engine and the a/p. Any piece of galvanised iron sheet would be worth trying. Some metals have bene especially concocted to be more permeable to magnetic field than plain iron If rememeber rightly one is called mumetal. Not that you could likely find it. I would suggest move the autopilot to the other side with a shorter or longer tiller arm to get that spacing.
Vic you mention spark plugs with inductive supressors. Now my ignorance is often shown on this forum but I did understand that it was built in resistor rather than inductor for supression. As also with spark plug leads having resistance. Piston engined aircaft have an earhthed shield screen around the plug and leads to reduce radio interference. Set me right VIc olewill
 
William_H said:
Vic you mention spark plugs with inductive supressors. Now my ignorance is often shown on this forum but I did understand that it was built in resistor rather than inductor for supression. As also with spark plug leads having resistance. Piston engined aircaft have an earhthed shield screen around the plug and leads to reduce radio interference. Set me right VIc olewill
Click to expand...

Commonly yes plugs can have a built in resistor as an interference suppressor. In NGK "R" plugs it is 5k.

OMC CD ignition systems do not work well with resistor plugs and require plugs with a low resistance inductive suppressor . I believe the Champion "Q" plugs, with inductive suppression, were developed specially for OMC engines. The equivalent NGK "Z" plugs are a later development .
Because NGK "R" plugs have often been supplied as equivalents of the Champion "Q", which they are not, NGK plugs have gained a bad reputation amongst Evinrude and Johnson outboard operators.

The official line at least until rebadged far eastern engines appeared as Johnsons and Evinrudes was that only Champion plugs should be used . although in the days of points ignition other brands were usually also listed. Other American brands that is, never NGK
 
Many thanks for all the responses.

To round things up I gave Raymarine a ring. They are always very helpful.

There is very little that can be done. The magnetism from the outboard is just too strong. I am unable to site the tiller pilot in any other place.

The only real way to deal with the problem is to site a remote compass . The Raymarine Compass System can shake hands easily with the Tiller Pilot and defaults naturally when connected. They don't make them any more because you get so much from GPS/Plotters.

Not to worry. It still works fine under sail . Being single handed it was very useful under power to put up and take down sails etc. Particularly
in congested areas which is mostly the case.

I will revert to locking the tiller over and going round in circles slowly . Funnily enough, in a small boat that has limited access and slanting decks, this takes more time than a bigger boat. Sails, seven fenders, four marina lines plus keeping a look out sometimes has to be done in stages.
 
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VicS said:
Thats quite surprising . I explored the field around my E'rude with a small compass while not running. At one point the compass swung through 180 and pointed south.
Click to expand...

The Evinrude/Johnson flywheel has if I remember correctly 2 magnets set into the inside of the circumference. Here they pass the pick up coils both for ignition and lighting. So magnetic field from the o/b will be much dependant on where the flywheel stops. On the other hand we might expect the flywheel to always stop on compression so perhaps it does always stop with a magnet in one location. If on the other hand stopping point is various then we would expect the magnetic interference and direction of interference (magnetic field ) to be variable. So having started this reesponse I am not sure but might be worth Vic checking if he is going boating or OP checking for interfence with engine stopped but at various positions of the flywheel.
Further thought if the engine stops on compression that might be near the point where ignition coil is aligned with a magnet which might give the best magnetic circuit throug the coil iron so minimum magnetic field compared to any other place except where lighting coils are which might also minimise magnetic field. What am I trying sayI dunno. all very interesting. (theoretically)
olewill
 
William_H said:
The Evinrude/Johnson flywheel has if I remember correctly 2 magnets set into the inside of the circumference. Here they pass the pick up coils both for ignition and lighting. So magnetic field from the o/b will be much dependant on where the flywheel stops. On the other hand we might expect the flywheel to always stop on compression so perhaps it does always stop with a magnet in one location. If on the other hand stopping point is various then we would expect the magnetic interference and direction of interference (magnetic field ) to be variable. So having started this reesponse I am not sure but might be worth Vic checking if he is going boating or OP checking for interfence with engine stopped but at various positions of the flywheel.
Further thought if the engine stops on compression that might be near the point where ignition coil is aligned with a magnet which might give the best magnetic circuit throug the coil iron so minimum magnetic field compared to any other place except where lighting coils are which might also minimise magnetic field. What am I trying sayI dunno. all very interesting. (theoretically)
olewill
Click to expand...

That's interesting.

With the tiller pilot in it's normal position , and in standby mode, the compass reading is quiet with the engine off.

If the engine has just been turned off, it takes a while to quiet down.

I will check though with the flywheel in different positions.
 
LONG_KEELER said:
Many thanks for all the responses.

To round things up I gave Raymarine a ring. They are always very helpful.

There is very little that can be done. The magnetism from the outboard is just too strong. I am unable to site the tiller pilot in any other place.

The only real way to deal with the problem is to site a remote compass . The Raymarine Compass System can shake hands easily with the Tiller Pilot and defaults naturally when connected. They don't make them any more because you get so much from GPS/Plotters.

Not to worry. It still works fine under sail . Being single handed it was very useful under power to put up and take down sails etc. Particularly
in congested areas which is mostly the case.

I will revert to locking the tiller over and going round in circles slowly . Funnily enough, in a small boat that has limited access and slanting decks, this takes more time than a bigger boat. Sails, seven fenders, four marina lines plus keeping a look out sometimes has to be done in stages.
Click to expand...
Do you get the same effect with the charging circuit disconnected?
 
You should be able to pick up the old M81190 Seatalk fluxgate on EBay etc for around a hundred quid or so . That will solve the problem entirely if correctly sited

Raymarine do still make and sell compass transducers but not for Seatalk 1 and therefore not directly compatible with the ST series tiller pilots

(and to pick up a minor technicality, chart plotters, GPS etc cannot supply heading information)
 
lw395 said:
Do you get the same effect with the charging circuit disconnected?
Click to expand...

Hi LW

I don't have outboard charging. Just a solar panel. The boat came like that.

My starter battery is now my right arm ( with the left as a back-up). Charges well on beer and burgers. . :)
 
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