vampire outboard!!!

[Gerry]

Can anyone help me. I have a Yamaha 4hp 2stroke outboard, its always been very reliable until this week! Works fine during daylight hours but as soon as night falls , nada, nothing zilch! Starts first pull in the sunlight but after dark not a breath of life! I've changed the carburetor, cleaned all the connectins and fed it new petrol, all to no avail! Do I need to string it with garlic do you think? Am in the caribbean at the moment and thought maybe it could be down to humidity but that is pretty low, under55% even at night and the temp difference is only about 10 degrees F after dark. I am getting desperate, the row from Galleon Bay to Nelsons Dockyard is getting longer and longer.... HELP!

 

[Lifeboat]

I would have put it down to temp change,if it works ok in the day when it's warmer but is no good at night, but you say that the temp change is low, so i dont know. Sorry!

You could try new plugs.

 

[Lakesailor]

Yes the temp change must be the clue.
The fact it used to work OK and now doesn't sounds like a crack in the HT side of things. The slight lowering of temp and the marine environment causing a little condensation in the HT circuit. (Similar to a cracked distributor cap on an older petrol engined car - do you remember distributor caps?)
Have you blathered it in WD40? That would be a start.

 

[pessimist]

Shine a torch on it?

 

[cliff]

Before you go sloshing WD40 all round the place, remove the cowling and try to start her at night and look for any stray arcing or sparking on the HT side. I does sound like a condensation problem combined with a crack in the ht side or a perished HT lead or a duff spark plug or.........

Good idea to fit a new plug while you are at it but do look for flash over on the ht side - should be visible at night.
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[William_H]

Don't rely on seeing the HT leakage as a spark in the dark I reckon it could be leaking try cleaning all the wires. Try also checking the HT lead plug connection to ground with multimeter should be in the range 100 ohms to 1000 this of course is not leakage but the conduction through the coil winding. olewill

 

[supermalc]

In my youth I was taught a good 'bodge' for a weak spark was to close the plug gap a little. Cars with points usually had a 25th gap, and simply gapping to 20, the thickness of your thumbnail, usually overcame any starting woes, usually in the winter.

I had an A series 1100 engine with larger pistons, so more compression. Started in the morning, went to work, started at lunchtime, came home, wouldn't start to return to work. In the end I closed just 1 plug in frustration, and it started perfectly. I didn't realize we carried this handy 'feeler gauge' until I started work using micrometers in factory some years later.

I tell this little tale as an example of how small a difference it takes to overcome the spark. In the above case, simply the wear to the plugs with a 3 mile journey.

P.S. an expensive 'sports coil' beyond my finances would have solved the problem.

 

[Gerry]

Many thanks for these thoughtful suggestions. I am trying them all. Meanwhile, despite 'refreshing' the fuel I have found an additive called 'Fresh Start' for stored petrol and the engine has started twice at night - so maybe it was something as simple as stale fuel. Does this make sense?

 

[Gerry]

Many thanks for all these suggestions. I will try them all. Meanwhile I have added some liquid called 'Fraeh Start' to the petrol (recommended for petrol that has been stored too long) and the engine has now started twice in the evening. Could it be as simple as poor petrol?