Charging circuit on Yamaha outboard has stopped working.

[fredrussell]

My much loved and endlessly trustworthy Yamaha F8 fourstroke outboard has a 6 amp charging output. Sometime over the last season it stopped outputting any charge. Is this likely to be fixable by the humble home mechanic or is it likely to be a pro job?

Any diagnostic tips or advice would be much welcomed.

 

[VicS]

My much loved and endlessly trustworthy Yamaha F8 fourstroke outboard has a 6 amp charging output. Sometime over the last season it stopped outputting any charge. Is this likely to be fixable by the humble home mechanic or is it likely to be a pro job?

Any diagnostic tips or advice would be much welcomed.

Probably the rectifier/regulator has failed

Too expensive to replace without confirming its failure. See page 7 et seq of the CDI electronics Troubleshooting Guide. http://www.cdielectronics.com/wp-content/uploads/2016/12/7th-Edition-Troubleshooting-Guide_RS.pdf

Unless you use the outboard a lot the best/ cheapest / most effective solution might be to fit a solar panel instead

 

[fredrussell]

Cheers Vic, will have a look.

 

[rotrax]

Cheers Vic, will have a look.

If it is a single phase alternator the rectifier/regulator will have three wires, positive and negative plus one from the charging coil.

A motorcycle " pattern " rectifier/regulator will be much cheaper.

Ebay or Google is your friend.

A simple continuity test down the coil wire to earth might be worth doing, in case the coil has a bad connection or is open or short circuit.

 

[AngusMcDoon]

My much loved and endlessly trustworthy Yamaha F8 fourstroke outboard has a 6 amp charging output. Sometime over the last season it stopped outputting any charge. Is this likely to be fixable by the humble home mechanic or is it likely to be a pro job?

Any diagnostic tips or advice would be much welcomed.

Might be the rectifier as Vic says, but another common culprit is a connection somewhere. Go through them all under the hood. It's simple to do & costs nowt.

 

[William_H]

Yes rectifier itself is unlikely to fail especially intermittently. However wires and connections are all susceptible in marine environment. Check every thing closely. olewill

 

[VicS]

If it is a single phase alternator the rectifier/regulator will have three wires, positive and negative plus one from the charging coil.

A motorcycle " pattern " rectifier/regulator will be much cheaper.

Ebay or Google is your friend.

A simple continuity test down the coil wire to earth might be worth doing, in case the coil has a bad connection or is open or short circuit.

ITYWF that it ill have at least four wires . Two from the (lighting) coil ( green ) a positive and a negative . The negative will be grounded to the engine block

The coil itself will not be earthed so the continuity test must be done between the wires coming from the coil.

The OP has not fully identified his engine but this is the part which fits many F8 motors

..... http://www.bhg-marine.co.uk/yamaha-68t-81960-00-rectifier--regulator-5476-p.asp

 

[rotrax]

Just been in the shed and checked a pattern moped one. It has a three terminal connector, two horizontal, one vertical. It is specified for a Suzuki. Perhaps the case is used as earth.

Anyway, the pre 2004 retail price sticker is still on it, £7.99.

If one could be used, it would be cost effective.

In most motorcycle units, one end of the coil is earthed. To measure continuity and resistance you measure down each coils output wire. Measuring between the wires shows short circuits.

 

[VicS]

Just been in the shed and checked a pattern moped one. It has a three terminal connector, two horizontal, one vertical. It is specified for a Suzuki. Perhaps the case is used as earth.

Anyway, the pre 2004 retail price sticker is still on it, £7.99.

If one could be used, it would be cost effective.

In most motorcycle units, one end of the coil is earthed. To measure continuity and resistance you measure down each coils output wire. Measuring between the wires shows short circuits.

But the OP is asking about his outboard engine, not his motor cycle

I'm sure though if you can suggest a suitable motorcycle rectifier/ regulator and provide instructions on how to modify or adapt outboard wiring to suit it the Op will be very grateful

If he was prepared to accept a non regulated DC supply a simple bridge rectifier such as https://www.rapidonline.com/dc-components-kbpc3502-35a-200v-bridge-rectifier-mb352-47-3226 coulbe be fitted for little more than £1. The coil output would go to the terminals marked AC the _-ve terminal would be grounded to the engine block and the DC + would be taken from the + terminal.
I used something similar on an outboard that was only fitted with a lighting coil.

 

[rotrax]

The simple CDI ignition systems and single coil charging circuits will be similar in operation to moped/motorcycle ones. The unit I have, speced for a Suzuki, would no doubt rectify and regulate with the case eathed, the pos and neg to the battery and the other terminal attatched to the coil output. The extra Yamaha wire might need to be earthed, if it is the other end of the coil.

Otherwise, buy the correct unit, no doubt at some expense.

 

[fredrussell]

Wow! £180 for the Official Yamaha part. Me thinks a bodge is coming on! Will update. Thanks again for replies.

 

[VicS]

Wow! £180 for the Official Yamaha part. Me thinks a bodge is coming on! Will update. Thanks again for replies.

You get so little charging from a small outboard unless you run it at highish revs and for prolonged periods that I agree with not forking out for a new OEM rectifier

I used to have to take my battery home periodically for charging despite having , in theory, charging from the outboard.

I fitted a small ( 5W) solar panel and that now takes care of all the charging. You'll see the panel on my boat pictured on the Marlec brochure at https://www.marlec.co.uk/wp-content...Lite-Solar-Brochure-011015.pdf?v=79cba1185463