rev tacho help

[xs 400]

i have a 30hp yam 2 stroke 2002 , i tried to add a yam rev counter 6 pole analog today and nothing. i added a positive from battery to rev counter so batt to rev , ground to rev counter was negative from battery, send was green from outboard, started up outboard and ........nothing?

help

[Poly]

Multimeter time:

dc Voltage (20 V scale) between POS and Ground
ac voltage (20 V scale) between SIGNAL and Ground

Stupid question - is the battery connected to the engine?

[mister p]

Originally Posted by xs 400

i have a 30hp yam 2 stroke 2002 , i tried to add a yam rev counter 6 pole analog today and nothing. i added a positive from battery to rev counter so batt to rev , ground to rev counter was negative from battery, send was green from outboard, started up outboard and ........nothing?

help

did you connect the rev counter to the same boat that the engine is on?

[xs 400]

thanks guys!

info..yam 30hp two stoke pull start man tilt therefore no battery.
second hand yamaha 6 pole un adjustable rev counter.

polwart 1st...........what i tried was adding a 12v battery into boat .

positive battery to rev counter positive
negative battery to rev counter ground
blue wire on outboard to rev counter send

started up nothing checked connections, checked battery fine

mister p........... yes

[Poly]

xs 400 - if I am reading that correctly you only have one wire connecting the engine to the gauge - ie. the battery is a standalone power supply not connected to the engine. I don't think that will work, the tacho is measuring pulses of voltage (probably not the right term). For their to be a voltage there must be two connections. Normally the ground (battery negative) is also connected to the engine ground and so provides the second connection.

If it were me I would attach engine ground to battery negative and see where I get to. However there may be some reason I've not thought about why that is a bad idea - so I'd hang on and see what other folks suggest.

N

[EnglishLes]

I think you would need to connect positive, negative (ground) and exciter wire from the engine to the rev counter. If your Yam has an alternator then you might need a rectifier to ensure that you produce DC and not AC. As this would produce a pulsed current the rev counter may give misleading readings. This might be when a battery would need to be connected.

[jyasaki]

Originally Posted by xs 400

positive battery to rev counter positive
negative battery to rev counter ground
blue wire on outboard to rev counter send

Won't work. You've got no reference between the battery and the engine. Tie the battery (-) to a point on the engine block, and see what that does.



jky

[9D280]

Originally Posted by xs 400

i have a 30hp yam

Originally Posted by xs 400

blue wire on outboard to rev counter send

I may be wrong here, but I think Yams use a green wire for the Tacho signal.


If it's a pull start engine, does it even have an alternator to hook the tacho up to? - Outboard tachos count the pulses from the alternator, not the pulses to the spark plugs. It's unusual for a pull start engine to have a charger circuit, although some do for auxiliary lighting etc.


Follow your Blue wire back to the engine. it should end at a small black box with three terminals - one with a red wire (or nothing if you don't have a battery to charge), the other two yellow* wires dissappear up under the flywheel. Your "tacho signal" wire should share one of the yellow* wires' connections (the two halves of the AC out of the alternator), and the battery & engine will also need a common ground.

If you don't find something like that, tell us where the blue wire finishes. Post a pic or six if need be!


Edit:

* these two wires might be green - I am having a mental block between Yam & Merc... Either way, they dissapear under the flywheel!

[xs 400]

I think your right, I beleive send is green, bit of a slip on my part i first said the send was green, then in a later thread Blue? sorry

as far as an alternator, it has a (2p) socket for lights on the front
and my hand book says alternator output 12v 80w?

is this ac?

the consensus seems to be i need

send ....rev counter send back to female green on outboard
earth....rev counter back to earth black on outboard.
battery....rev counter back to ?


question do I have to add a 12v battery to have a rev counter ( as man start and man tilt I dont have one, and would prefer not to .

can the battery go straight back to red positive on outboard?

[Poly]

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. It shouldn't be a major issue to add a regulator/rectifier if the lighting circuit is unregulated.

If you want to keep the battery separate then:

Signal - Green wire from engine
12V Pos - Battery positive
Ground - to both engine ground AND the battery negative

It may be possible to wire it direct to the red and black connections at the engine but it will depend whether the power output is properly rectified (dc) and regulated - otherwise you may just fry the tacho.

[9D280]

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....

[xs 400]

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

[9D280]

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.

[xs 400]

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?

[Poly]

Originally Posted by xs 400

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.

[9D280]

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?

[Poly]

Originally Posted by 9D280

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...

[xs 400]

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?

[9D280]

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.

[xs 400]

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!