Johnson 4HP "AC Lighting"

[joe17]

Johnson 4HP \"AC Lighting\"

I have a Johnson 4HP outboard from approx 1980. It has a 3 pin outlet labelled "AC Lighting" on it. I measure the output from this when running the engine and it was between 3 & 4 volts AC.

Does anyone know what use this is?

The Clymer Evinrude/Johnson shop manual doesnt say anything about it.

 

[oldharry]

Re: Johnson 4HP \"AC Lighting\"

Not a lot of use! Magneto ignition outboards often have an extra coil fitted to provide a low voltage source from which to run a light or something similar for night use (boats under 5m need only show an all round white light), and this is what this is intended for. There is no control so that at low speeds the voltage drops and the light goes dim, while at high speed you blow the bulb..... Many of them are supposed only to give 6 volts anyway, so they arent much use for battery charging via a rectifier either.

Not much use for anything really.

 

[davey]

Johnson outboard AC lighting

I have a Johnson 4HP outboard from approx 1980. It has a 3 pin outlet labelled "AC Lighting" on it. I measure the output from this when running the engine and it was between 3 & 4 volts AC.

Does anyone know what use this is?

The Clymer Evinrude/Johnson shop manual doesnt say anything about it.

I think that the proper voltage only occurs when the motor is running at 3000 rpm or higher. I also suspect that the AC output is three phase. In this case one needs a three phase rectifier (six diodes). One easy way of making up a three phase rectifier is to buy two single phase bridge rectifiers (the very common types GPB35 only cost about £2 each on eBay) Some electrical knowledge is required. Charging output is said to be about 5 amps. It is also possible to buy a $77 kit from Crowley Marine. Allegedly the kit contains everything including the 3 pole connector.

 

[rotrax]

Not a lot of use! Magneto ignition outboards often have an extra coil fitted to provide a low voltage source from which to run a light or something similar for night use (boats under 5m need only show an all round white light), and this is what this is intended for. There is no control so that at low speeds the voltage drops and the light goes dim, while at high speed you blow the bulb..... Many of them are supposed only to give 6 volts anyway, so they arent much use for battery charging via a rectifier either.

Not much use for anything really.

Hi, A cheap motorcycle three phase rectifier can be found for not much money on EBAY and will work fine. Otherwise the resistance of the bulb filaments must be calculated against the output so that natural impedance causes the generating coil or coils to become magnetic,so canceling the permanent magnets in the generator and allowing the output to settle where it wont blow bulbs. Hope this helps.

 

[davey]

Outboard Lighting Coils

Not a lot of use! Magneto ignition outboards often have an extra coil fitted to provide a low voltage source from which to run a light or something similar for night use (boats under 5m need only show an all round white light), and this is what this is intended for. There is no control so that at low speeds the voltage drops and the light goes dim, while at high speed you blow the bulb..... Many of them are supposed only to give 6 volts anyway, so they arent much use for battery charging via a rectifier either.

Not much use for anything really.

These lighting coils on small outboards are often identical to the ones used on mopeds. As to bulbs blowing when the moped was racing downhill, that problem was solved at least fifty years ago. A choke was fitted in the output wire of the generator. Now as the engine goes faster, the output voltage rises as more magnetic flux is being cut per second. The frequency of the AC also rises hence the impedance of the choke increases. The problem is that the choke has to be matched to the current draw of the bulbs but this is not a problem for the moped factory. OK this is a fairly crude method of regulation but it is better than nothing.

If perchance one has an outboard with a six volt lighting coil all is not lost. Whilst rewinding the coil would be an extremely bad idea there are other ways. One method is to use a charge pump, also known as a voltage doubler (capacitors and diodes are used) Another way is to use a transformer (or to save size and weight an auto transformer). The transformer need not be fitted inside the motor, it can be on the boat. Same goes for the charge pump. Owing to the low current that is produced a voltage regulator may not be necessary (on boats the problem will usually be flat batteries not overcharged batteries) Even one ampere can be extremely useful on a sailing boat as modern LED lighting needs very little current.

 

[Ubergeekian]

These lighting coils on small outboards are often identical to the ones used on mopeds. As to bulbs blowing when the moped was racing downhill, that problem was solved at least fifty years ago. A choke was fitted in the output wire of the generator. Now as the engine goes faster, the output voltage rises as more magnetic flux is being cut per second. The frequency of the AC also rises hence the impedance of the choke increases.

All alternators (AC generators) are self-limiting in this way - you don't need always or even often need a choke because the coil impedance is enough. That, for example, is why bike light systems have alternators instead of dynamos - it allows them to light bulbs at 3mph and not blow them at 30mph.

 

[VicS]

I have a Johnson 4HP outboard from approx 1980. It has a 3 pin outlet labelled "AC Lighting" on it. I measure the output from this when running the engine and it was between 3 & 4 volts AC.

It is an AC supply for lighting!
Not actually three phase as suggested but it does need a six diode ( 3 phase) rectifier to use for battery charging.

At running revs you should get in excess of 12 volts between the Yellow/grey and either the plain yellow or the yellow/blue ( I dont know what to expect between yellow and yellow/ blue and I have never measured it.)
You wont get much at idle speed!

AFAIK OMC did not use 6 volt coils.

The diagram below illustrates how to connect lights directly and the circuit for a suitable rectifier that you could make from individual diodes.

Alternatively you could fit a four wire rectifier and a charging lead directly. But the rectifier would probably cost you around £40-£50. ( $47 in the USA)

There almost certainly was, maybe still is, a battery charging adapter incorporating a rectifier, that would have plugged into that socket ... but you would not want to know the price!

 

[davey]

AC generator regulation

All alternators (AC generators) are self-limiting in this way - you don't need always or even often need a choke because the coil impedance is enough. That, for example, is why bike light systems have alternators instead of dynamos - it allows them to light bulbs at 3mph and not blow them at 30mph.

Hi, I don't want to be pedantic about this but I think the use of the word "ALL" is a rather bold statement! If one examines moped wiring one will often find a little choke mounted somewhere on the frame. This is needed because the bulbs are non linear resistances. They are low resistance when cold but high resistance when hot (lit). Unfortunately the brighter they get, the higher the resistance they become. Without some kind of regulation the bulbs are liable to pop like flashbulbs. I have seen this happen to cyclists descending steep hills with their "dynamos" on (bicycle "dynamos" are invariably alternators). The cyclists do get a wonderful light for a few hundred yards, then phut! Incidentally there are now some quite small 12 volt vehicle alternators coming onto the surplus market as vehicles are scrapped. The Nippon-Denso compact alternator as fitted to the Suzuki SJ413 and other vehicles is nominally a 25 amp machine and it is so small that with some GRP work it could easily be bodged into the power hood of most outboard motors. By the way modern bike lights use LEDs with voltage regulators built in.

 

[davey]

3 phase rectifiers on eBay

It is an AC supply for lighting!
Not actually three phase as suggested but it does need a six diode ( 3 phase) rectifier to use for battery charging.

At running revs you should get in excess of 12 volts between the Yellow/grey and either the plain yellow or the yellow/blue ( I dont know what to expect between yellow and yellow/ blue and I have never measured it.)
You wont get much at idle speed!

AFAIK OMC did not use 6 volt coils.

The diagram below illustrates how to connect lights directly and the circuit for a suitable rectifier that you could make from individual diodes.

Alternatively you could fit a four wire rectifier and a charging lead directly. But the rectifier would probably cost you around £40-£50. ( $47 in the USA)

There almost certainly was, maybe still is, a battery charging adapter incorporating a rectifier, that would have plugged into that socket ... but you would not want to know the price!

I have just bought one of these for about £7.50 including airmail.

http://cgi.ebay.co.uk/3-Phase-Diode...al_Components_Supplies_ET&hash=item230ead7ccd

The 10 amp version costs £1 less and would be OK but I don't like to run components near their limit. Anyhow I liked the diagram of how to wire six diodes even though I already knew it. Rather curiously if you were to measure between any two wires, the voltage would be the same! (its to do with the analogy of the Isle of Man legs or the three legged man on the specially made bicycle!)

 

[VicS]

I have just bought one of these for about £7.50 including airmail.

http://cgi.ebay.co.uk/3-Phase-Diode...al_Components_Supplies_ET&hash=item230ead7ccd

The 10 amp version costs £1 less and would be OK but I don't like to run components near their limit. Anyhow I liked the diagram of how to wire six diodes even though I already knew it. Rather curiously if you were to measure between any two wires, the voltage would be the same! (its to do with the analogy of the Isle of Man legs or the three legged man on the specially made bicycle!)

The figure I was quoting was for an OMC part as would be fitted to an an outboard with DC battery charging output ... as is fitted to my Evinrude in fact.

Nice to know there is a less expensive alternative. The 10 amp one would be more than adequate as the max output is probably only 6 amps, if that, but for a £1 difference what the hell!

I think you are wrong about the voltage being the same between any two wires. It's not a three phase generator. There are only two coils and they are wound on the same armature. So the analogy with the Three Legs of Man does not apply. The yellow/grey wire is from the junction of the two coils and the other two from the other ends.
A two legged man on a bicylce where the two pedals are only narrowly spaced apart perhaps

Thats why the wiring for AC lighting is as it is shown A simplified representation of the page in the manual which I have now scanned:

 

[davey]

Charging from Johnson outboard

Very useful drawings that must be extremely rare. The motor in question is a 7.5HP which has a different magneto from the 4HP AFAIK, its not here so I cannot look at it. As the three phase rectifier is now ordered I may as well use all the wires as there may be harmonics that can be rectified as well. Denso now use four diode pairs on their Y connected alternators. Each phase goes to a pair of diodes but so does the star point! It is planned to use a NASA LED anchor light which only draws 200 milliamps so as long as some power is created it will be a great help. Many thanks for sharing the information.

 

[VicS]

The parts catalog show the same battery charging kit for a 1980 7.5 as a 1980 4 hp but no indication as to what the AC lighting coils were.They may have been different to the charging coils.

All the info online is for models sold in the USA. Models for the European market were often slightly different in some of the detail and made in Belgium.

But yes if you have three wires out to an AC lighting socket connect them all up to the AC input terminals of your rectifier.

The OMC rectifiers had the negative side of the output grounded to the case but its up to you I would think whether to ground your negative or not.

 

[William_H]

Lighting from an OMC OB

The supply is designed to run lamps. Low voltage means dim lamps which doesn't matter much.
However if you want to charge a battery then you must develop a voltage greater than the terminal voltage of the battery. ie in the region of 13v DC to get anything into a battery.
One way which can help a bit to improve the voltage is to use Schotky diodes. These have about 1/3 of the volty drop of silicon diodes. So the rectifier will have your DC going through 2 diodes so you lose 1.4 volts while a schotky at about .25 volt drop will only lose .5 volt.
I got schotky diodes out of an old computer power supply. They usually have 2 double diodes fitted. PM me if you want more advice here. You can buy them from electronics supplies.
Either way you won't get much out of an outboard. Mine will charge at .3 amp at high revs using a silicon diode bridge. This might double to .6 amp with schotky diodes. So I don't bother. In fact I don't bother with o/b.
Now to use the lighting coils on LEDs might be far more successful. Fit the rectifier and a capacitor to make it smooth DC. (not vital) Measure the voltage that you get at usual revs. Then wire in LED bulbs with a suitable resistor. If you get 8volts DC then you can run 3 LED bulbs in series with about 2.5 volts dropped per bulb. at typically 50 ma bulb current from the bulb spec you need 10 ohm series resistor.
Now fit a Zener diode from + to -ve rated at 8volts at several watts. This diode when wired backwards ie not conducting direction will start to conduct at an excess of 8v (there are a huge range of voltages available) This will waste current so keep voltage at close to 8volts should you increase RPM above cruise. A resistor perhaps 10 ohm in series might save the zener from going to heaven on really high revs.
It will all take a bit of fiddling top get the right values. Adjust the LED series resistor to get the current specified for the LED. If you can't get enough current hence brightness then use only 2 bulbs in series. You can fit many sets of LED bulbs and series resistors in parallel as current drain is low.
To use a 12v rated LED replacement lamp you will not get enough brightness unless your o/b produces 12v or more. good luck olewill

 

[davey]

AC lighting on J8BALCSS Johnson Seahorse

Thanks to everyone for all your help. I'm still trying to source the 4 pole male connector that fits the outboard motor socket but its not listed even on the American websites. There must be one somewhere on the planet but the problem is finding it. Really it needs to be IDd with a part number first. The other way is to fit a fresh plug and socket, duh!

 

[VicS]

Four pin connector ??

Not the same 3 pin part # 0594110 used on later models ?

You won't want it when you know the price. You'll figure another way of doing it

Fixed wiring harness and a 3 pin Dri-plug and socket on the boat?

If you must have then try Willsmarine in Kingsbridge or Oakley marine in Brighton

 

[davey]

Johnson outboard AC lighting progress

I'm slowly making progress on this but job #1 was getting a connector to fit the motor. After weeks of getting the run-around I have now got a plug that fits so no butchery is required! The plug I bought seems to be a clone of a Hella marine plug that was bought on eBay as a 4 pole deck plug. Possibly the genuine Hella item is the one listed as Hella AUS 2744 by Hella Australia. So much for the stories about these plugs being Johnson specials, you just can't get the right staff any more.

 

[davey]

Johnson outboard AC lighting progress

I'm slowly making progress on this but job #1 was getting a connector to fit the motor. After weeks of getting the run-around I have now got a plug that fits so no butchery is required! The plug I bought seems to be a clone of a Hella marine plug that was bought on eBay as a 4 pole deck plug. Possibly the genuine Hella item is the one listed as Hella AUS 2744 by Hella Australia. So much for the stories about these plugs being Johnson specials, you just can't get the right staff any more.