rectifier wiring 30hp tohatsu

[Wazfish]

Hey,

A mate of mine has just wired a rectifier onto his 30hp 2 banger tohatsu, the rectifier seems to be doin what its suppose to but when the motor is reved it pumps out 30+volts and thats only at half throttle, is there something else that needs to be wired up to keep the voltage at a constant charging voltage of about 12.5v or whateva it is? any help is appriciated

Cheers
Waz

[groverwa]

Without seeing the cct of the output of the OB and the way it has been wired I tend to think that it has been wired up as a VOLTAGE DOUBLER

Can we see the cct to help further

See http://www.hobbyprojects.com/the_diode/voltage_doubler.html as an example of the method to double the output voltage of an AC source

[Wazfish]

what do you mean by cct?

[groverwa]

Sorry

cct means circuit - wiring diagram

[Swamp]

Hi, try this and see if it helps. The wiring diagrams are towards the end.

http://www.tohatsu.com/tech_info/own_man_pdfs/Toh25C2_30A3.pdf

Bill

[groverwa]

swamp

Can you now please get the wiring diagram of how he wired the diode in please??

Also why did he put a diode in ??

[tednted]

Gday Waz
Dont know what your mate has done But whem I used to have a 25 yammy 2 banger I just went to the motorcycle wrecker & bought a regulator/rectifier off a motor bike & it worked perfect with a max charge of 14.1 vlts . Rectifiers have to be regulated to send the correct voltage
cheers Al.

[groverwa]

If the circuit provided on the pdf document relates to your mates outboard the I cant see the need to rectify the output as this has already been done by the full wave rectifier - see http://en.wikipedia.org/wiki/Rectifier for a description - on the output of the magneto - see http://en.wikipedia.org/wiki/Magneto_%28electrical%29 for a description - and see attachments for the circuit diagram.

It does not make sense to rectify a DC voltage - the rectified output from the outboard will have a certain AC component as explained in the Wikipedia description - which, if rectified again may add to the original DC voltage to give you the effect that you are getting:-/

If the output voltage needs regulating then just a regulator is required if the voltage increases too much

Hope this helps but please get answers to my other questions and whatever we can find out will help other members in the future

Mike

[skipalong]

do you need a regulator kit

[BM]

30V output from the stator windings is fairly normal. Having a load across that (a battery) pulls that voltage down quite a bit. Older outboards often only had a rectifier fitted (Mercs for example).

You could use a 3 pin regulator from an electronics supplier to regulate your max voltage (although most of these are fairly low current handling) or as mentioned pop into a motorbike shop and buy a rectifier/regulator. They start around $60-80 and go up from there.

Cheers

[bignense]

It sounds like there is a grounding problem and the voltage is 'floating" rather than being tied to ground(negative).
Try testing between a bare bolt or something similar (bare metal) on the motor and your positive. According to the above wiring diagrams the work is already done for you and you should already have a 12VDC(or there abouts) output between the Red wire and the Black(ground). Unless you are running some very sensitive electrical equipment you shouldn't need to do any more to it as if connected to a battery the Battery will act as a capacitor and absorb any differences and spikes produced. I have an 18HP tohatsu and I fitted a $5 Bridge rectifier found in any electronics shops, as my motor did not have one installed, and I haven't had any problems.
PS. sorry if this is an over simplified reply.

hope this helps

bignense

[bignense]

Just to add another step to your testing or if you actually do need to install a Bridge rectifier to your motor as i did, you should have 12AC across (between) the Yellow and White wires coming from the magneto.
This then passes through the bridge rectifier (the square thing) and the output should then be 12VDC(or close enough) between Red and Black. There will always be a slight AC side to this but as i said in my previous reply if connected to a battery this shouldn't worry a thing.
If you somehow wire the rectifier the wrong way you may end up with funny voltages so maybe that is what has happened.
The 2 AC wires(Yellow and White) go on diagonally opposite sides of the rectifier and the 2 DC wires(red and black) go on the remaining pins.
If you need a hand finding the appropriate bridge rectifier ill be happy to help but if you ask at any Electronics shop they will show you how its done(unless your unlucky enough to get the work experience kid).

Once again sorry if this is over simplified.

Good luck

bignense