Misfiring Watermota crossflow.

If you have an alternator, check the small wire on the back of the alternator is connected.  Also check the bulb and that 12V is being supplied to the bulb.  Most alternators on our boats need to be excited to produce current, this excitation is supplied by the warning light circuit.  If the bulb is blown or the lead has become detached - then you will have no light and the alternator will not produce current.

Stephen, no ignition light is probably a fault in just that, as M says, it's usual for the ignition light to come on when the key is turned and go OFF when charging.
It could be something as simple as a loose or bad connection in the lamp unit, a sharp tap will often bring it back to life ! Mine has done that in the past and the simple remedy has sorted it, hopefully yours ditto !!

JIML - You're explaining that an alternator requires an initialising current via the warning lamp circuit, and once generating no longer takes the current from the lamp circuit.  You gave me the clue to research it further and it seems the current is actually reversed - pushes back - to the point that the lamp gently extinguishes! I never knew! Full exposition here:-  

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I hope it is as simple as changing a bulb: I expect to have to grope under the alternator. My fear is I blew a diode (See Surge Quench Diode note) because when I was having engine trouble I switched the charging, with engine running, between batteries via the changeover switch without hesitation when even that can be the moment of death - instantaneous soaring voltage - for an alternator set-up if that protecting diode, if fitted, had ever previously been sacrificed. Groan ....

current only travels from one high voltage to a lower one. Its the fact that the rotating dynamo/alternator generates an emf (voltage) that feeds onto the  previously 0 V end of the bulb that means there is no longer a voltage across the bulb and hence no current flows through it once the generator up and running. A blown diode would affect overcharging but not necessarily affect the ignition light. I say not necessarily because I would need to examine the cct diagram to be sure.

If you do need to replace the lamp do not use an LED because the current won't excite the alternator.

L
Hi ...bit late for this but I don’t get this tickling the alternator stuff. An alternator works by having fixed DC current stator and a multicoil rotor that operates to slip rings rather than commutator to provide an AC output that is then converted to DC via a diode bridge. There’s no tickling AFAIK (although I confess to not understanding the meaning of tickling in this context) and the warning light function is not a dependency of the alternator function. Sorry BB but don’t agree.

Have you been reading the info in my link earlier? I'm no technician and its all new to me but I found it all a model of clarity. Machine sensing and Battery sensing and the maintenance of the wiring as a normal routine I found easy to understand and regarding optimum battery charging success it explained a lot. Because I have a friend with a narrowboat I was familiar with the reference to (optional) advanced Voltage Controller/Regulator which few cruisers such as ours would likely have with our limited power needs/no inverter or washing machine. 
I noticed too that the article had a reference to what a diligent BSS inspector could be looking out for. All relevant and I hope the whole thing all correct?

Have a read of this http://arrc.ebscohost.com/ebsco_static/repair-tips/8852CH12_The_Warning_Indicator_Light_or_.htm and this https://www.howacarworks.com/ignition-system/troubleshooting-the-ignition-warning-light which also covers a dynamo system.

The LED issue is well know in the classic car world. It's an easy thing to check.

Minerva, the ignition light function is to 'excite' the windings, if no ignition light when switched on then no charging will start.
Stephen, if your diodes are blown you would know about it from the smell !! Fried electronics !! Don't ask !!

It's relatively easy to replace the diodes they come as a unit, l also changed the rectifier while l was at it. There are kits on eBay

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Ok guys...I will need to come back to this one. I am interested in electrics and studied it years ago ...but I confess I didn’t read the links and I need to focus now on boat prep for the tidal challenge. This will bug me now! I am one of those people that needs a circuit diagram to understand it. I will read the links later if I survive the tidal! Cheers

A wonderful forum this, driving both body AND mind to greater things! Great good luck with the tidal challenge and don't forget the 30 metres!

Minerva wrote:Ok guys... if I survive the tidal! Cheers

You're in the best company so you will be fine !  Good challenge, only wish I was 20 years younger, or 10 would do !

Members may recall even from last August I was reporting my fuel problem and my pre-crossflow refusing to run except intermittently after me running my fuel low. Since then I changed almost everything, bought loads, and consider myself an expert on re-setting the fuel float-level in my sleep. It was recommended! 
In fact I have had no further use of the boat at all while I variously tried new approaches or waited for help. A garage-owning contact sent his tame mechanic. 'Fantastic chap, knows Ferraris downwards, classic vehicles, nothing he cant do, he's the best'. Turned up, sat in boat for 10 minutes, went away, phoned two weeks later to say he had gout and never returned. No offence to present company but its my impression that a) marine engineers are now doing inspection work - less tiring than working, or b) are self-employed for a reason, unemployable - poor attitude and won't be told, and probably no good anyway!
I'd become very despondent and resigned all winter.  But last week I thought to go through everything once more before facing the overwhelming task of removing and cleaning the fuel tank. I put in a new LT wire direct from the points to the coil with no connectors. Lo and behold engine, instantly, ran like a new one. Am so relieved. 
So, just as another member had wisely quoted, 'fuel problems' are usually electrical! I'll re-license her after all!

Yes Stephen. I am sure there are many examples out there of a lowly dry joint resulting in all sorts of unnecessary expenditure on cheap Chinese electronics, new sports coils and all sort of other unnecessary purchases.
I still think the replacement condensers are rubbish though.

You can add crappy spade connectors to that list. They snap inside the insulating cover and cause intermittent failures. Difficult to trace until you do find a couple and now it's the first place I look.

Its all a process of elimination.  Good spark, Fuel, compression, Fire.  It may not be the correct process but I would unscrew fuel line from Carb. Push on a length of tube and stick it in a bottle.
Crank the engine for 10secs, if the bottles empty you have a problem with the fuel supply.
Perhaps now is the time to sort out the ignition. Change the whole lot for electronic, new dizzy, Leads and plugs.
If your not confident, find someone who is. The trouble with tinkering is you are never quite sure if you solve the problem.
I'm confident around the crossflow engine, they are pretty basic, but if you do get a problem it can sometimes be a pain to diagnose as I found last year.
The Alternator does need tickling, it gets this through the ignition lamp. LED bulb useless, I think the bulb needs to be minimum of 3 watts. If the ignition light fails to come on pre start, the Alternator will not output!

You're quite right about the alternator initiating current through the ignition warning lamp - the traditional filament type of course. I don't necessarily agree about transistorised ignition unless you want to be on trend and desperate to spend your money. Our under-stressed low revving engines work perfectly well without, even if old distributor rusty inside, providing the wiring connectivity is intact, and I should know!

Sure, but when you consider for the money spent you get a new distributer, points, coil, rotor arm, capacitor, leads, coil and new plugs that seems like an awful lot of problems you can cross of your list! A spark at the plugs doesn't guarantee ignition.

Point (no pun intended) taken. However as I am the man who has now bought all those things to no new effect, along with a good many others like needle valve, alternator (I'd blown it) and so on, I'm stuck with what I've got, (and already had, as it turned out, in working condition), and now quite happy. For other people your advice is good!

Stephen wrote:Point (no pun intended) taken. However as I am the man who has now bought all those things to no new effect, along with a good many others like needle valve, alternator (I'd blown it) and so on, I'm stuck with what I've got, (and already had, as it turned out, in working condition), and now quite happy. For other people your advice is good!

I guess at some point we all travel the same path.