Outboard Rectifier

[jmp]

I have a rectifying rig for my Johnson 15 HP O/B. The unit has 4 wires emerging (red,yellow ,yellow/blue,and yellow/black)into a harness.From the harness is a 3 pin plug to outboard,and a twin black/red to battery.

I would like to use the rig on an Evinrude 6 HP,which I beleive is the same as Johnson.

The problem is that the outboard socket is only 2 pin! Can anyone tell me the secret vis a vis 2 or 3 pin from the AC supply,and can I use the same unit,and if so which wires go where?

Thanks in anticipation.

Michael

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[steve_cronin]

This is more to stimulate a reply from others than an answer in itself:-

I seem to remember having this set up on an evinrude/Johnson (OMC) some years ago. As I recall, the reason for three output pins/sockets is that it caters for half and full charge. I daresay that if i saw it the wiring up would become plain but on a simple set up you should have the lighting coil going into the rctifier on digonally opposite terminals and the rectified DC coming out on the other two usually the red & black for positive and negative.

Steve Cronin

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[jmp]

Thanks Steve.
The rectifier is a cast cylinder with a steel insert,like a coreplug in one end and the 4 wires emerging from a resin type filler at the other.The wires are in a bundle.
Ihave opened the harness to find the black is a continuous run from the casting mount to battery!

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[VicS]

I have an Evinrude 6hp and I have had a quick look at the rectifier. The red wire is DC +ve, the black wire is connected to the rectifier casing and is DC -ve. Obvious so far but the AC side is not as simple as expected. I expected to see two wires coming from the the engine but there are three, as you have oberved, coloured yellow, yellow/blue and yellow/grey. I can only guess that there are three coils connected in star or delta configuration giving a 3 phase AC supply hence the 3 wires. Just like a car alternator in minature.

I did not see your post earlier this evening and at around mid-night I dont feel inclined to investigate any further but I will check it out a bit more tomorrow and let you know what I find.

The 15hp engine may have had a higher electrical output but that shouldn't matter. If your 6hp (mine is the Yacht twin) only has a single coil, with just 2 wires coming from it then you can just connect them to any 2 of the yellows on the rectifier. If I'm right about the three phase arrangement that is.

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[ccscott49]

Are you sure the output from the 6 hp is AC? It may well be DC if there are only two connections. If it is AC, then it ios single phase and easy to rectify, with a simple bridge rectifier, I cant draw one here, but it's a very simple circuit and easy to find in lots of places.

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[Alex_Blackwood]

If you have three wires coming out of the engine to the rectifier they can be checked thus: With a multimeter on the OHMS scale check between each wire if the readings are equal between all three then you will have a three phase output without a neutral. If the reading between one wire and either of the other two is half of that between the other two then you probably have single phase and neutral.
In the first instance the voltage between all three wires will be equal ie 12 volts.
In the second instance the votage between the two phase wires will be 12 volts and between either phase and neutral will be 6volts. (All figures approx.)!
I must admit that without seeing the system much of the above is guess work based on probability so please don't blame me if it is totally different. It would be interesting to know the outcome though!
It could also be that one of the wires is an earth in which case you will geta reading between two wires only with the third being earthed to the engine.
If it is a 3phase system if you put your meter across the wires to the rectifier you should get a reading from all three wires to ve and open circuit to -ve with the meter leads connected one way round and a reading from all three to -ve with open circuit to ve if you reverse the meter leads.
If single phase and neutral you will get similar but only between the phase wires and the nuetral, possibly only between one phase wire and neutral. Again without seeing the set up it is difficult to tell.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by Alex_Blackwood on 16/08/2003 12:11 (server time).</FONT></P>

 

[andyball]

can't help but think that lot 'll confuse 'em....even assuming a meter capable of measuring low resistances so accurately. Also most digital meters need setting to a "diode test" setting to make your rectifier test work.





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[VicS]

Re: Further investigation

As promised last night I have had a further look at the charging circuit in my Evinrude engine.

The rectifier does indeed appear to be a 3 phase full wave unit, but careful resistance measurements indicate a single centre tapped coil ( not three coils as I first suspected). Yellow and yellow/blue are the end connections while yellow/grey is the centre connection. This would be in agreement with the wiring diagram in the owners manual for the standard 6hp engine (no rectifier) for powering various combinations of lights.

My thoughts are:
(i) are you sure that there are only two wires in your engine coming from the lighting coil and not three like mine?
(ii) like ccscott, are you sure there is not a rectifier already fitted?

If as you say there is just a simple AC output, provided it is not earthed, all you need is a suitably rated bridge rectifier from some where like RS components (That is precisely what I used with my previous engine). However, you would obviously like to use the rectifier you have, in which case connect it as I suggested in my previous post and just isolate the spare wire.

Perhaps I should say that the Yachtwin is based on the ordinary long shaft engine but amongst other differences it has a rectifier built in to give a (small) DC output for battery charging

Final comments:
As andy says measuring low resistaces with a multimeter is not easy because the connections to the meter can have more resistance than the item under test but allowing for that I got 0.3 ohms between yellow/grey and either of the other two and 0.6 ohms between the other two.
Also as andy says I needed to use the diode setting on the meter to check out the rectifier.

Do let us know when you've sorted it all out



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[Alex_Blackwood]

Re: Further investigation

That makes more sense! I agree with both Vics and andy about the meter but most modern meters will give a good reading of low resistance, after all we are not looking for Bridge Megger accuracy and most modern meters have a diode function but a meter on ohms range will still give a low reading in one direction and a high in the other when connected across a diode! I was brought up in the days before multimeters and diode test settngs. You could perform wonders with a dusty old AVO and a set of "croc" clips! and a bit of wire of course!
My theory about the neutral is manure! After writing that screed at the gallop and straight of the top of my head I sat down to do the circuit and of course it will not work. It could only be three phase output.
I would be a bit reluctant to use the existing rectifier on single phase if it was designed for three, it could alter the current rating and cause more trouble than it is worth. As suggested you can get them from RS or Maplins at reasonable prices.
Mounting them in a suitable environment would need consideration.


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[jmp]

Thanks everyone for the response which was excellent,if not complex to a one such as I.
I now have the problem of trying to understand the technicalities ,and will report back when i have investigated further.

Regards Michael.

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