yamaha charging lead

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nyx2k

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ive just got a dejon 14 dayboat with a yamaha 9.9 2stroke manual start. the engine is a 1991 and i need to check if the charging circuit works and how many amps it gives. what sort of lead do i need to connect the engine to the battery and do i just use a cheap multimeter to check if the charging is working

kind regards nick.
 
Do you know if there is already a rectifier fitted to the engine? I don't know about Yamahas, but for some engines this was part of the charging "lead" - needed before you can connect a battery.

Do you have a manual for the engine which would give the charging output?

Andy
 
The first thing to look for is any polarity indication on the output socket. If it is marked with any indication of positive and negative then you have a DC output, if not then probably just AC.

If you have a multimeter you should be able to use that to determine whether or not you have a rectifier fitted.

If you check the output socket with the meter on an ohms scale you will get the same low reading whichever way round the meter is connected if there is no rectifier but if there is one you will get a high resistance one way and a low resistance the other. You do this with the engine not running.

With the engine running and the meter set to DC volts (20volts say) you should not get a reading, at least not a sensible one, if there is no rectifier. If there is a rectifier then you will get a sensible reading which will be speed dependent, rising well above 12 v as the revs are increased.

It might be sensible to do these checks with a small load, a 5watt bulb for example, connected.

Inspection of the engine itself should reveal the rectifier if fitted. If the leads to the output socket can be traced back to the casing below the flywheel without any other components being involved then there is unlikely to be a rectifier fitted but if you can trace them to a small "component" from which other leads go off to the the above casing then that is most likely the rectifier.

I would be surprised if a manual start engine had a rectifier fitted but it might (my 6hp Evinrude does have but that is a model specifically intended as a sail-boat auxilliary). An electric start one probably would have.

If you find you do not have a rectifier then you have two options. Buy a suitably rated bridge rectifier from Maplin or the like and include that in the connection between battery and engine, or buy a retrofit or chaging lead from your dealer.

Take care to connect the battery with the polarity correct. Connecting it the wrong way it will be instantly fatal to the rectifier and also maybe the coil! Also do not connect the battery until you are certain you have a rectifier or you will destroy the coil.
 
thanks very much for the info.
i'll check it in the morning with my multimeter. if the output is ac will the correct lead convert it back to 12dc for battery charging.
regards nick
 
It certainly looks like it but it would be better if someone more familiar with Yammies could comment. Ideally one would like to know its part number and then confirm that it is the right part for the engine in question, but if they are anything like Johnyrudes then one part fits a whole range of engines.

Take a look to see if there is anywhere obvious that it coud be mounted and connected to the existing wiring, or indeed if you already have one fitted! It's the "component " I referred to in my earlier reply. The two green wires will be the AC input and the red and black +ve and -ve output respectively. The negative is, as I would expect, intended to be grounded to a convenient screw on the engine.

I do not know how much they cost new, several tens of pounds probably, but it might be sensible to find out before bidding. At least you have got nearly 6 days to investigate

Don't think you are going to get masssive amounts of electrical power You'll probably only get around 5 or 6 amps maximum, maybe less, and then only when the engine is running at fairly high revs
 
i'll have a check for rectifier price and for the proper lead which i presume may have a rectifier inline somewhere to convert to 12v dc.
i only need power for a few lights but i suppose i could buy an led torch or similar to use on my 110ah leisure battery. i'll be running a small electric cool box in the spring and summer which draws 5amps. so it will run all day without charging the battery. the boat will stay in the driveway in the winter and launch off the trailer but will be on its mooring in the spring and has no shorepower.
 
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