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Old 24 January 2012, 04:36   #11
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OK, You have alternator.

Follow the two wires back from the plug on the front of the engine. One of them should go to ground (bolt on the engine block or similar). If the other goes to a small black box like I described, you got rectified DC.

I assume you are mounting the tacho in your console? Two options might be to get a small 12V "gel" battery from maplin (other electronic component vendors are available!). Or fit a voltage regulator. (again, cheap as chips for the sort of current a tacho will pull)

Some of the "black boxes" have regulator built in, but as Pol says, unless you can get that confirmed....
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Old 24 January 2012, 12:40   #12
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tacho help

thanks guys!

pol i like your idea " Personally I'd look at adding a small battery to the boat and wiring it in so it is charged by the engine - then it can run vhf/sounder/chartplotter/gps or other gadgets you might want to add"

and 9d i like yours " I assume you are mounting the tacho in your console? YES
and to get a small 12V "gel" battery from maplin, AND CHARGE IT AS ABOVE

so wiring for batt and charge?

Signal - Green wire from engine
12V Pos - Battery positive
Ground - to both engine ground AND the battery negative
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Old 25 January 2012, 04:45   #13
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Almost. And apologies if I have misread your description)

Assuming you want tacho & Battery charging:

Green from engine to tacho "signal" as discussed.
Two wires (+ / -) from charging socket to battery.
+/- from battery to tacho +/-"power" terminals. (2 wires)

This works because the -ve from battery to engine is the same -ve that the tacho signal is referenced to in the engine, and so puts all the -ve terminals at the same potential. It also means you are only running three wires from engine to console, and keeps the worst of the spaghetti in the console!

It is also worth putting a battery isolator on the + wire between the battery & everything else.
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Old 25 January 2012, 12:50   #14
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yamaha tacho advice

thanks for that!

rang a Yam dealer today they reckon about 50 for a lead from outboard socket to charge battery.

They told me it probably didn't have a regulator/rectifier and they are coming back to me with a price.....but sounds expensive

how could i check if it regulated/rectified?
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Old 25 January 2012, 16:34   #15
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thanks for that!

rang a Yam dealer today they reckon about 50 for a lead from outboard socket to charge battery.

They told me it probably didn't have a regulator/rectifier and they are coming back to me with a price.....but sounds expensive

how could i check if it regulated/rectified?
I bet the socket is a standard size you can get much cheaper - or access the back of to connect direct to the terminals.

Someone who has done it will be able to comment better but you should be able to get a regulator/rectifier for a motorbike/scooter etc cheaply. If you wanted to you could house it in a box inside the console which would keep it dry/protected.

Simplest way to know if it is rectified is stick a multimeter in the outlet with the engine running. If it gives a signal on a.c. but not d.c. it is unregulated. If the voltage changes a lot as you rev it then it is probably unrectified - someone else can probably give you a better idea of voltages but if it goes over about 14.5 volts it is probably unregulated.

Adding a battery, isolator switch etc can start to add up if you are on a budget. Five years ago I bodged a solution for mine which is still in place today. Basically I got a "car jump start pack" and joined the leads to the cables from the engine. This gave me: battery, box to house it, isolator switch, cigarette lighter socket, battery monitor scale, and a cheap (crappy) charger for less than the cheapest battery I could buy. Not necessarily a particularly "marinised" solution but hidden in my console its been fine - since (like mine) your electrics are not really safety critical it might be worth considering. After 5 years of neglect I have had a completely dead battery (in storage) and will probably replace it soon - but not decided if I do the same or do it properly.
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Old 26 January 2012, 09:05   #16
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Originally Posted by Polwart;
Simplest way to know if it is rectified is stick a multimeter in the outlet with the engine running. If it gives a signal on a.c. but not d.c. it is unregulated. If the voltage changes a lot as you rev it then it is probably unrectified - someone else can probably give you a better idea of voltages but if it goes over about 14.5 volts it is probably unregulated.
Wot you been drinking man?

Signal on AC but not on DC = Unrectified
wildly varying voltage = Unregulated


>14.5V comment - agreed.

A visual way of assesing rectified or not is to follow the wires from the socket. If they go straight to somewhere under the flywheel, chances are it's AC, but the rectifier could be hidden under there, so dig out your meter. If however one (the red) goes to the flywheel via a black box (one other terminal of which should have your green Tacho signal wire on as well) then it's rectified. With modern electronics it may also be regulated in that box, but you'll need to find a Yam expert for that.

Unless you are removing the engine at the end of every day, you could remove the socket completely & fit a big grommet instead. - got a pic of it?
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Old 26 January 2012, 09:49   #17
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Wot you been drinking man?

Signal on AC but not on DC = Unrectified
wildly varying voltage = Unregulated
Ah well I may have had a little toast to the bard, with some HP sauce... but thats another thread...
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Old 26 January 2012, 16:27   #18
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rectifier

handbook suggest 2p socket ac for lights 12v 80w output.

also says that if i want to charge battery i need a "special " wire

also says that if I connect to 2p to run lights the battery wont charge.
if i want to charge battery, wire lights to battery not 2p socket which suggests my outboard has both ac output and dc from the red wire?

two green wires far right come from socket, with a spare green socket (rev send?)
then go to the left up under flywheel, but also into what looks like reg/rec and red wire comes out (pos dc charge?)

followed the two green wires from the 2p socket seem to go into what looks like a rect/reg see pic (grey with fins ) out of this is a red wire! which yam say is a positive which makes sense.

what do you think?
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Old 27 January 2012, 10:03   #19
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80w AC - that's about right for three 21W bulbs + an instrument / cabin light.


OK, just to check I'm reading this right:

You have two green wires from the socket go to under the flywheel and also to a box which also has a red wire that at present is just hanging, and one of those green wires has a spare socket connected to it?

If so, that red wire is your battery charge, and the green is "tacho send". To sanity check, put your meter on DC V on a scale 0-20V DC across the red & any non painted bolt on the head, you should get something higher than 13V DC (I forget the min voltage that is needed to actually charge the battery, but it is >12) If you then do the same with the green, you should get next to nothing on DCV, but something between 8-20V AC. Values wooly as your meter is calibrated for 50Hz, the alternator changes frequency with RPM... and I've no idea how your meter will handle the variable frequency.


The book makes sense if it's wired like that - add lights and the electricity will go for the path of least resistance - i.e the lights - so not a lot will be left to feed the rectifier etc. You could use a 3 core cable to the console (get a nice chunky 15A if you use domestic cable - keeps the losses down) then a couple of red bullets (blue wonlt fit the Yam bullets) from your local car parts store for the R & G cables, and a suitable eye to go under one of the head bolts - job done.


Another option as your engine doesn't need it to stay aive is a cheap small car battery. My boat has had a minimum spec 40 bought 'coz it was avaialble at nanoseconds notice near where I was at the time battery in the console. That way if you do go for bigger electrics (e.g VHF / Nav. lights / electric start) you are future proofed. Probably not much more expensive than the big Maplin Gel batts if you shop around.
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Old 27 January 2012, 15:17   #20
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tacho help

thanks so much 9d and pol i feel ive learned so much, i appreciate your time!
if your ever in the southwest i'll buy you a pint!

of to maplins to buy a multimeter but i think weve cracked it!
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