Mariner/Yamaha

BarryH

BarryH

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I've an old Mariner, yamaha base engine, twin cylinder 20 hp. I use it for pottering and the odd fishing trip on the little boat. I've never had cause to worry about charging off of it before. Now I need it to charge a small capacity battery.
There is a wire from the magneto. Its not connected to anything and by looking at the manual its the output for charging. What I need to know is what sort of rectifier/regulator is needed. I can't see the thing putting out much more that 16/17 volts at full whack. It'll more than likely be ac output I would have thought.
The manual gives no specs on it or what type of reg/rec is needed. I've spoken to Barrus and they say that the original part is no longer available.



My Initial idea is to use a readily available rectifier from a motorbike. Most of them now run a 12 volt leccy system so should be ok there. What about regulating the voltage. I know a batt will tolerate 14/15 volts,but what about when the engine is running fast for a period? I don't want to kill the echosounder/electrics that will be connected. Anyone done this before that could give me a few pointers or any weekend sparks out there got any ideas?

edited 'cos I can't spell or type

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<P ID="edit"><FONT SIZE=-1>Edited by BarryH on 04/11/2003 00:10 (server time).</FONT></P>
 
been there & done it with an 8hp yamaha. Try a search for several previous posts.

But....yes it'll likely be ac & need rectifying.

moped rectifier ok up to maybe 2 Amps (the tiny ones,maybe 1" x 1 1/4" , two connections only.), or a maplin ( & many others) bridge rectifier, contains the necessary + rather more capacity for £2 odd.

Even say 30W of power will eventually get over 15V on a battery bank (within a few minutes at higher rev's with 80W coil + 150AH bankwith my 8hp).....but regulators are ££ from outboard shops & couldn't be doing with sourcing a suitable m/c one, so I used to switch the nav lights on if using 3000+rpm for more than a few mins.

Something from a Honda vision or similar wd cope, but hard to be specific w/o wiring diagrams for donor machine 'cos it's ages since I looked at one...also some don't actually regulate , despite being named "regulator/rectifier" in parts book.

Many marine electronics will cope with more than 16V , but if no spec on yours then try to keep below that.



Hope that helps a bit.


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17v is ok

Barry I wouldn't worry about the output voltage. I have had many large Merc outboards that were unregulated and so I always had 17.5V across the battery terminals with the engine running. I did this for hours and hours at a time, and the batteries still lasted years, no problems. I asked my Merc dealers and they said not to worry. I always used unsealed batteries rahter than the sealed for life types becuase i thought they might need more topping up, but I dont think they did much in practice

Modern electronics will be fine as you know, they tend to be 9-30v or similar. On older ones you have to check the specs

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Just spoke to the tecchy dept at Barrus. More than helpful they were. They informed me that the system is a 6amp system. Thats at wide open throttle. The lower the revs the lower the amp output. JFM was right in saying that they didn't really bother with regulation on that age of engine. The rectifer module for the engine is still available at a cost of just over 200 quid! I want one but not that badly!

So I've 2 red wires coming out from the magneto. Not heavy gauge wires. Looking at them I'd say they're 1.5-2.0 mm. What do you reckon they're for. One is obviously a charge output or are they both charge outputs? Maybe one is a lighting coil output that doesn't need rectifing, dunno. What do you think?

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Hi Barry
One may be a rev counter feed? Any chance of finding/borrowing a "Haynes" type workshop manual - I found one for my old Evinrude and there were several wireing diagrams which were spot on and good enough for me to make up a complete new wireing loom.
Regards mikej


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Both wires are red. I would have thought that a tacho would take its feed from one of the trigger wires for the coils. I'll have a play with a meter at the weekend and see if I can electricute myself.

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Having thought some more....most m/c regulators are meant for a single or 3-phase alternator....with 2 or 3 wires from the coil, none of which is earthed , so probably won't work on your o/b (can be done with some, but hit & miss). A few bikes had a 12V AC regulator for the headlamp circuit (eg. Honda mtx125) which would do the job.Also some scooters have a nice AC regulator with a charging output for the battery which wd be ideal, I'd think.

An old-fashioned -'ve earth zener diode also ok, as on some 12V british m/c's.

Think I'd connect up via the cheapest rectifier diode you can find, to a fully charged battery & see how much spare power there is- you may find as I did that leaving a light or two on is all it takes to keep the voltage below 15V when running at speed for any time.

I see there's now two wires ! if so it may be a proper single phase alternator (if NO continuity from either one to earth, but low resistance(under 2ohms) between the two, then v.likely). In which case a small reg/rect from a scooter/bike shd be perfect

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Ok, on reading your last post it prompted me to dig out the multimeter. The two red wires show no continuity to earth, ie flywheel or any part of the engine block/pwr head.
There is a low ohmage reading, 0.75 ohms across the two wires. I've a rectifier knocking about from a TS185, dunno why but I have. I'll rig it up at the weekend when I can find a place to earth the rectifier. Hopefully it should work.



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sounds right....the TS185 unit may not have a regulator in it; but you'll soon know.

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Ok done it. Wire'd in the rectifier and made up a jury rig harness to the battery for now. Run the engine in a tank and took my life in my hands and started it up. At tickover to about quater throttle it registers 11.7V. From quater to half it gives just 0over 12V. From half to full throttle it rises from just over 12V to max of 15V.
I think that with those results I'll not bother with a regulator.

If I use a big enough batt it should take a few volts over without doing any damage. There'll be something running off of it to take care of those extra volts anyway. Had to stop messing with it as one of the neighbours complained, which seems pretty academic seeing as its like world war 3 out there with all the fireworks. Now all I've got to do is sort a suitable plug and socket for the engine and make up a proper harness for the battery cables. Dou you think I should put a fuse in line. It seems prudent to do so.

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Fuse? always a good idea in case the diodes fail (tend to have 'em on bikes & not cars). If suzuki ts185 ones are as reliable(not) as gs550/750 you'll need one (totally different units,don't worry).

The voltages were w/o a battery connected ? sometimes you see more with one (depending on size/flatness etc), but as you say,switch something on.

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