Outboard voltage

[popeyethesailor]

Hi Can any one help me with this

Outboard is

Ex rnli mariner 2 stroke 40hp

I have noticed on the newly installed volt meter that the voltage is going up with rpm to 16 volts!
I assume it's the same as a car and should Limit to 13.8v

Am I right in thinking the rectifier is knackered ?

I have just put in another one 2nd hand from eBay and that is exactly the same


Any help much appreciated

Thanks Stuart

[popeyethesailor]

Just found this on the net


"I've just fitted an identical one to my Mariner 15. This engine has a stator (like the al;ternator on a car) under the flywheel which puts out alternating current (AC) and if you want to charge a battery you need to convert it to Direct Current (DC) That is what the rectifier is for - you now should have DC power flowing out of the rectifier with the red lead being positive to the battery + terminal and returning from the negative terminal through the engine casing to earth (ground). You should check this with a voltmeter between the red cable and the engine case and you will find an output voltage of between 10 V at idle to about 18V at full revs - you may need to fit a voltage regulator to limit this top voltage to 14 V or 15V so as not to damage 12V instrumentation run off the battery such as VHF radiio, fishfinder etc."



I am now thinking it is only a rectifier with no regulator!

[Nos4r2]

take a pic of the rectifier unit and post it-I should be able to tell you what you've got.

[HughN]

I have protected each piece of electronics with a 7812 voltage regulator (about 50p each) but there is a thread on here somewhere about using a motorbike regulator...

[popeyethesailor]

Originally Posted by Nos4r2

take a pic of the rectifier unit and post it-I should be able to tell you what you've got.

These seem quite common on older outboards Stanley de4204

I cannot find any spec for this on the net I think now it is only a rectifier

Thanks

[popeyethesailor]

Originally Posted by HughN

I have protected each piece of electronics with a 7812 voltage regulator (about 50p each) but there is a thread on here somewhere about using a motorbike regulator...

Hi thanks just looked on eBay biggest was only rated at 1.5 amp

What did you use on your radio?

[HughN]

There are a couple of other versions. I used a 78S12 which is 2A, but I should probably have gone for the 78T12 (3A).

They do get quite warm at times; a nice bit of metal nearby was a convenient heatsink... ...don't blame me if they burst into flames.

[popeyethesailor]

Originally Posted by HughN

There are a couple of other versions. I used a 78S12 which is 2A, but I should probably have gone for the 78T12 (3A).



They do get quite warm at times; a nice bit of metal nearby was a convenient heatsink... ...don't blame me if they burst into flames.

Thanks
Out of interest if you are still running your mariner 30 do you know what voltage it was kicking out to the battery ?
The rectifiers I have are the part used on the older mariner 30's

[Peter_C]

I put a motorcycle regulator/rectifier into my outboard to control voltage. It is not really important on brand as they will function if it is compatible with the boats current electric system. In other words it could be from a PWC, snowmobile, motorcycle, garden tractor, etc. Rectifier alone will smoke an AGM or gel battery very quickly, as the voltage goes too high.

[jyasaki]

I assume you have a battery installed? If not, that's your problem. Loading the output will pull the voltage down a substantial amount.

jky

[popeyethesailor]

Hi yes lead acid car battery fitted next step is to try some load on the circuit and see what happens

[HughN]

Originally Posted by popeyethesailor

Thanks
Out of interest if you are still running your mariner 30 do you know what voltage it was kicking out to the battery ?
The rectifiers I have are the part used on the older mariner 30's

I'm now running the Yamaha version of the same engine. At some point I'm going to put an oscilloscope on the various wires and seem what is happening - my tacho has stopped working and needs troubleshooting.

[paintman]

13.8 on a car is indicative of a faulty alternator.
This from another forum:
"Correct proceedure is ......
take vehicle for a short drive with everything turned off and on return without stopping engine and with everything turned off raise the engine speed to 2-3000 rpm and check the battery volts .. should climb to 14.4v as a minimum.
If not 14.4v the voltage regulator is faulty ...a voltage reg that only reaches 13.6v will give you about 6 months battery life."

ETA. I've checked this on our own cars & that's also what I get.
I've not tried the boat & must remember to try it & see what I get - but that won't be for a while.

[Nos4r2]

Originally Posted by popeyethesailor

I think now it is only a rectifier

It is only a rectifier. It is worth putting a rec/reg unit on-it's less likely to fry any electronics if you suffer a battery switch failure while running.

Give Electrex a call.

[popeyethesailor]

Originally Posted by Nos4r2

It is only a rectifier. It is worth putting a rec/reg unit on-it's less likely to fry any electronics if you suffer a battery switch failure while running.



Give Electrex a call.

Hi thanks I have sent them a email they will prob come back with there universal one being suitable,
Out of interest where did you find out the spec of the Stanley unit?
I spent hours trying to get info on it on the net with no joy

[Nos4r2]

I recognise it

[jwalker]

Since you're bugring about with your system, it might be worth noting that if you measure the output from a rectified but not regulated source it will be bumpy DC you are reading on your meter. Your meter will, therefore, not display a correct voltage unless you switch it to the AC range. Once you connect your system to a battery, you can consider it to be smooth DC (but it will still have a bump to it.).

[jyasaki]

Originally Posted by jwalker

Since you're bugring about with your system, it might be worth noting that if you measure the output from a rectified but not regulated source it will be bumpy DC you are reading on your meter. Your meter will, therefore, not display a correct voltage unless you switch it to the AC range.

Won't read correct then either. The output will be pulsed DC, but the AC meter will read half the peak value, smoothed to RMS of the waveform; somewhere around 40% or so. It is useful if you know what you're looking for (much like a car "test light" that comes on when connected to anything over about 9V.)

jky

[jwalker]

Originally Posted by jyasaki

Won't read correct then either. The output will be pulsed DC, but the AC meter will read half the peak value, smoothed to RMS of the waveform; somewhere around 40% or so. It is useful if you know what you're looking for (much like a car "test light" that comes on when connected to anything over about 9V.)

jky

Well that's how we measure AC! As an example, our UK mains is nominal 230v AC but the peak voltage is around 330v. Your figures are out too but I take the point you are trying to make.

[jyasaki]

To clarify: Most meters on AC will center the waveform for reference, then read RMS (rather than peak.) Which is why you can get an accurate AC reading of an AC component riding on a DC voltage.

Since you're talking about a rectified AC stream, the reference point (normally zero volts when reading AC) will be something less than half the peak voltage value (due to the area under the curve on either side), and the reading will be based on that.

The RMS factor is based on a pure sinewave waveform, so any deviation from a sinewave will read wrong. The resulting "AC" waveform in your case will be rounded pulses further apart than sinewaves on top, and closer to a squarewave on the bottom. Throws everything all wonky.

jky