Outboard Ignition - Points and Condenser

Lakesailor

Lakesailor

Well-Known Member
Joined
15 Feb 2005
Messages
35,236
Location
Near Here
Visit site
I'm helping someone sort out a Johnson Seahorse 5hp outboard that dates from 1966. It is a twin and there is no spark at either plug.
I removed the flywheel and found this....

seahorse.jpg


I've cleaned and set the points at 0.02" as it says on the flywheel. Using my multimeter I've established that there is continuity from the baseplate to the red terminal from the coil (disconnected from the points) and no continuity from the baseplate to the green terminal from the condenser (also disconnected from the points) the points make and break continuity between the baseplate and the isolated points terminal.
These checks are the same for both sets of components.

Are they as you would expect? Is there another test I can do to check which component is stuffed?
I am testing for HT by putting the flywheel back on and pulling the motor over with a plug grounded, and also by using an HT tester (one of those clear plastic thingies you stick between the lead and the plug.

Still no spark. I'm not very good on ignition. What to replace first. Is it worth the bother?
 
To spark well, magnetos are dependent on good, powerful magnets in the fly-wheel, they might have lost something in 43 years and a good speed of rotation, ie a strong right arm. That's all I can suggest.
Add, If you're brave, hold an HT lead, or better still, get someone else to do so, and pull the engine over at progressively faster rates. This will tell you if there's some life there. Sweaty hands aren't the best for this!
 
Not empirical testing, but the plug spanner took quite a bit of yanking to get off the flywheel magnets where it had stuck. /forums/images/graemlins/grin.gif
Turning over was done with the plugs out and a strong, long pull.
 
It is the coil and the one in the background is also cracked.
I don't know if that is symptomatic of a failure (like mucho heat inside) or just old age.
 
One of the tricks to get a lazy engine starting is to adapt a socket and spin the engine with an electric drill.It worked for me on an old Seagull engine.
 
But I don't have a spark.

I'm just going out to check for a circuit between the HT lead and the red terminal. It seems that an open circuit there is a bad thing.
 
Phil,

I've got a workshop manual for this......


Give me a chance to find it and the relevant bit and I'll give you some readings for the meter /forums/images/graemlins/grin.gif

AAaaaaagh
The WM is the idiot's guide to doing things. "Connect the S-80 or M-80 tester to the ignition..." No effin help at all. /forums/images/graemlins/mad.gif
 
With little doubt I'd say the coils are stuffed.





Should have added that there is a special tool for fitting coils so that the clearance from the flywheel magnets is correct.

But note very carefully or mark their positions (Flush with the edges of the mounts I think) befopre removing them and fit new ones in exactly the same position.


BTW your PM box appears to be full
 
It wasn't an open circuit. It showed a bit under 3K ohms on both coils. However, Vic has probably summed it up. /forums/images/graemlins/grin.gif
 
[ QUOTE ]
It wasn't an open circuit. It showed a bit under 3K ohms on both coils. However, Vic has probably summed it up. /forums/images/graemlins/grin.gif

[/ QUOTE ]

Don't give up just yet!! what you have measured is the sum total of resistances of the primary and secondary coils. ~ 3 Kohm for the secondaries seems in the right ball park. They are both the same which is encouraging. Try the primaries, red terminal to earth, with the points open. This might be just a few ohms. Try cleaning the CB points 'till they gleam. Try a slight gap variation either way. Magnetos are very fussy about condition and timing of their points, esp. for starting. Try a slightly smaller plug gap.
 
There should be no difficulty getting replacement coils.

not sure of the exact BRP part number, because I only have acces to parts lists from 1968 onwards but it seems they are interchangeable if not identical from 1950 to 1976. Part numbers that should fit are 580416, 582370, 582931, 582995, 584477. Price in the US around $28.60

Also CDI part number 183-4777 at $22.28
Sierra part number 18-5181 at $18.99
Mallory part number 9-23-102 at $17.99

These three are definitely listed for that engine
 
Is it a true magneto i.e. do those coils generate HT or is there a separate HT coil outside?
Agree those coils look dead.
You could try putting about 2A DC through the coil and see if it sparks when you interrupt the current (e.g with the points!). A 12V source and a 5 or so ohm power resistor might be a good current source. Don't let it over heat!
Assuming its not been put together wrong, the points need to open when the LT current is near a peak, I have seen this issue in a motorbike made of inconsistent bits!
You used to be able to get coils/magnetos rewound through the classic bike trade, I'm out of touch with that now.
Good Luck and try not to jolt yourself too much!
 
Hi Phill. The Johnson twins essentially had 2 separate magnetos one for each cylinder. Being 2 stroke engine one magneto is 180 degrees separated from the other under the flywheel.

A magneto works by having a magnet pass a coil in such a way that the magnetic field rises at the greatest rate at the time of spark needed.ie not when the coil is adjacent to the magnet but as it moves into or out the influence. This rate of change of field induces the maximum current in the primary winding which at the time has a short circuit presented by the points.

At the critical time of spark the points open causing the current to collaps in the primary coil. This change of magnetic field induces a large voltage in the secondary coil which is connected to the spark plug. The condenser (capacitor is used to provide a resonance with the collapsing current to give a better shaped current for the spark and to minimise point damage from sparking.

The most critical is the high voltage coil and if you have 5000 ohms from plug lead to ground that is a good start. However the high voltage can be finding a leak path through corrosion / moisture in the sealed (potted) coil.
Really the only way to test is by replacement.

The primary winding will measure much lower resistance which is reduced to zero when points make contact. You may not be able to discern the difference. So test by disconnecting the points. The condenser should show now conduction ie very high resistance but again is best tested by substitution.

As suggested quickly flashing a 12v battery across the primary should produce a healthy spark at the plugs. Points disconnected. But make it a very quick (short) contact as 12v could cook the coil with too much current.

There is not much else you can check assuming the magnet in the flywheel timing is fixed by the key in the flywheel and of course you have the correct plug lead for the correct plug.

The CDI ignition of later models is far better for starting but can fail with only replacement as the testing method. If he could find a wrecked 6HP it may be possible to convert. He will need the pick up coils under the flywheel 2 high voltage coils with plug leads and the electronics box.

The engine itself should be fine provided there is no corroded bolts snapped off and the gear lever is not to stiff. PM me on this one.
My old 6HP is still going strong 28 yo old. Perhaps because I have dismantled it so much. good luck Phil olewill
 
Not quite your problem,(those coils look stuffed), but we have one of those of similar vintage. It had been left on the rack for years by my wife's family because if you opened the throttle it gave you a hefty belt from the ignition. The ignition plate with all the gubbins on rotates to advance the spark and for some reason was badly earthed to the block. A wire strap between the plate and block cured it.
That advice about spinning it up to rejuice the magnets (from SOS) works a treat. I was given a mint 40plus, no spark. Works fine now.
A
 
Thanks Vic and you others. I tested the ground to red wire and after zeroing my meter it showed 1 or 2 ohms, so I reckon it could really be zero. I found coils at about $30 as well which means they will be £30 here. I have enquired at Wills Marine but I think it'll be too much for a small outboard without gears really.
I don't think he'll want to punt £30 per coil (plus points and condensers) on it.
What a shame though as it is immaculate otherwise. The strange prop may be a high thrust one.

Not bad for a 1966 motor though

seahorse2.jpg


seahorse3.jpg


seahorseprop.jpg


I have no doubt it will be appearing on ebay at a computer near you soon. Bargain if you have a scruffy runner already.
 
You must log in or register to reply here.

Share this page

Top