Power for navigation lights from outboard engine?

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labougie

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I have a little 12ft open dinghy which needs nav lights. The outboard is a 4hp Mariner/Mercury two stroke single pot from the 90s. Do I understand correctly that the outboard generates 12v AC? Can I tap off this, put it through a rectifier and draw 1 amp absolute maximum from it to power the lights without affecting the ignition system operation? Will a motor cycle type 12v rectifier do the job? Can I tap off anywhere on the engine I can find 12v AC? Thanks in advance.
 
Some outboards have "lighting coils" for this purpose, but 4hp is rather small for that feature. If you don't know that it has one, I think you can safely assume that it does not.

A smallish 12v gel battery via eBay (as used in wheelchairs, burglar alarms, jump start packs, etc) will be cheaper than trying to fit stuff to the outboard and will run a set of LED nav lights for ages before being taken home to recharge.

Pete
 
labougie said:
I have a little 12ft open dinghy which needs nav lights. The outboard is a 4hp Mariner/Mercury two stroke single pot from the 90s. Do I understand correctly that the outboard generates 12v AC? Can I tap off this, put it through a rectifier and draw 1 amp absolute maximum from it to power the lights without affecting the ignition system operation? Will a motor cycle type 12v rectifier do the job? Can I tap off anywhere on the engine I can find 12v AC? Thanks in advance.
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Small outboards may be fitted , either as standard or as an accessory, with a coil that can generate power for use for lighting ( without rectification to DC) or via a rectifier for battery charging. It is quite independent of the ignition system

Not sure exactly what model . Serial number & year would enable some info to be looked up/
but AFAICS generator coil and a rectifier kits are/ were available and were fitted as standard to the "sail" versions but the cost would be significant to now fit ........... The coil is $50 in the US and the rectifier over $100 without all the minor bits and pieces to complete the installation..


Single white around battery powered LED light is I am sure the way to go. .......... somebody makes them and a few years ago one of the West Country harbours ( Fowey ??) were flogging them to anyone they caught without lights!
 
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This

100173_1.jpg
........ http://www.force4.co.uk/department/...ed-light-with-suction-mount.html#.VciQz_lVhBc


Or this


100174.jpg
....... http://www.force4.co.uk/department/...nder-light-with-fixed-mount.html#.VciQ4PlVhBc
 
After seeing VicS's pix I've bought the suction cup all-round white - seems like the simplest solution. Thanks for everyone's input.
 
VicS said:
vry nice but 4 time the price!


100176.jpg
..... http://www.force4.co.uk/department/...avisafe-led-navilight-white.html#.VcjOTflVhBc
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Qualitee mate, qualitee..........feel the qualitee...:D When they first came out they were quite reasonably priced if you bought them from Scandinavia where I believe they originated, but as with everything boaty once the marketing people get hold of it and see how good it is....up goes the price and I suspect thats what happened here. They are a bit more sophisticated too if you look at their bi/tricolours which you can switch mode on.

They are perfect for a small yacht owner who doesn't want to put wires everywhere or go up the mast for the few times they need nav lights.

Tim
 
Just a quick comment on this:
Nav light.jpg
which I bought from Force 4.

The suction cup is brilliant - it sits on top of the outboard but vibration doesn't seem to affect it. However, in my 12ft open dinghy on the Thames, it's WAY too bright - it screws up my night vision forward and you can't see anything aft because of the dazzle. Fortunately, a wrap or two of white insulating tape round the lens and all is well - without it I'd have missed a evening trip up to Sunbury Regatta for the sail past and fireworks.

Thanks again.
 
Quite so the suction cup light is the best way to go. Do attach a lanyard to it just in case suction goes to stop it going o/b.
Just for those interested re charging coils. If it has a charging coil there should be a power outlet on the motor body. Also an additional coil (or 2) under the flywheel. ie additional to the ignition coil. (one for each cylinder).
The size of the coil is (or used to be) sized to feed 3x 12v bulbs probably 6w or so. But at high rpm. So fed on AC.
The makers also often made available a rectifier to turn the AC into DC to charge a battery. The charge depending on RPM. On the oold Johnson/Evinrude this did not produce much current into the battery as it needed to produce over 13v DC. This could be improved by using schotky diodes for the bridge rectifier rather than silicon diodes. I could get about .3 amp into a battery at normal lowish cruise RPM. With lights on this might rise a bit more.

Now if you wanted to run LED lights straight off the motor.... You would need the bridge rectifier as above feeding an electrolytic capacitor of 100 microfarrad or more rated at 25 volts or more. When you connect the LEDs the current draw will pull this voltage down. You would need to check witha volt meter just what the LEDs are getting. (if the lEDs are rated at 11 ton 30 volts you have no worries. Assuming they are cheap resistive current limiting then they could be demolished with too much voltage. (at high RPM.) a regualtor like a 7812 could be used to limit the voltage to 12v or a zener diode could be fitted across the supply. This will start bypassing current when voltage exceeds 12v. Needs a farly high power rating zener. Possiblky aslo needed a small resistor between the capacitor and the LED and zener. good luck olewill
 
Previous owner fitted a motorcycle battery, in the rear flotation chamber, with water proof hatch, then a 4ft pole with nav light attached on top, stops the white light getting in your eyes.
 
For info, a charging coil can be fitted to the Yamaha 4hp 2-stroke, I have one on mine, same goes for my Mariner 5hp 2-stroke which came with it fitted.

The parts used to be available for retro-fit from Ron Hale Marine in Southsea, I think they still are; easy to do except one has to remove the flywheel to fit.

I believe they give 3 amps; on ' saildrive ' engines set up for propelling cruisers like the Tohatsu 6hp one gets 6 amps.

I very rarely use the charging coil on my A22, the 30w solar panel gives all I need; but if motoring long distances in calms with the autohelm on it makes sense to plug in the charger.

That's for small cruisers, I do agree with the self contained simple light for a dinghy.
 
Seajet said:
For info, a charging coil can be fitted to the Yamaha 4hp 2-stroke, I have one on mine, same goes for my Mariner 5hp 2-stroke which came with it fitted.
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The workshop manual for my Tohatsu 9.8 calls it an alternator. I have always known them as charging coils. Maybe it's something lost in translation from Japanese.
 
AngusMcDoon said:
The workshop manual for my Tohatsu 9.8 calls it an alternator. I have always known them as charging coils. Maybe it's something lost in translation from Japanese.
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You might be a bit harsh on poor old Japanese translators. One might say it is indeed an alternator. It generates alternating current from magnet going past a coil. It might also be called a charging coil or a lighting coil implying one or the other. It seems that "alternator" as a name has been hijacked by the more frequently met alternator on a car. Certainly the english language is a flexible ever changing thing. olewill
 
William_H said:
You might be a bit harsh on poor old Japanese translators. One might say it is indeed an alternator. It generates alternating current from magnet going past a coil. It might also be called a charging coil or a lighting coil implying one or the other. It seems that "alternator" as a name has been hijacked by the more frequently met alternator on a car. Certainly the english language is a flexible ever changing thing. olewill
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You, and the translator, are both absolutely right. The Wiki page on magnetos...

It is categorized as a form of alternator, although it is usually regarded as distinct from most other alternators, which use field coils rather than permanent magnets.
Click to expand...

Learn something every day.
 
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