Need help with a spark problem

[Dave Barnett]

My son and I are in the process of restoring an old 9.5 hp Outboard Jet (brand) jet motor. F_R helped me find a site that gave us a lot of good info on the motor and we have it to the point that it should start. Our problem is spark. We have determined that the coil is in great shape. A crude (here hold this LOL) spark test proved to almost cause a loss of bodily functions . Both cylinders have good fire. I checked them with a voltage meter also and the output is about 50V set on DC 250 setting (el chepo meter) My 5hp generator in retrospect only puts out about 25V. Any way, all tested out fine untill I hooked up the spark plugs. I get no fire from the end of the plugs at all. No arc, nothing. I have good connections at the plug. I ran continuity on the plugs and they test fine. They are new plugs. (Champion C8J the same as the plugs we removed from it) The old plugs do the same thing. A nail inserted in the plug wire did arc on the block. It has been suggested that I have the wrong type of plugs and that could be but shouldn't I at least get an arc when The plug is grounded to the block like the nail?? I will greatly appreciate any help any of you all can give. Thank You and God Bless. Dave

 

[JB]

Re: Need help with a spark problem

Your post is confusing, Dave. If you have "a" good coil, are really getting "good fire" to both cylinders and measuring it with a meter (!!!) it makes no sense to me that the next sentence says there is no spark.

If we assume that your engine has a dual magneto there should be two coils and two sets of points to serve the two cylinders. Is this the case? If not please tell us what you do have.

I am moving this back to the Other Outboards Forum because we ordinarily consider ignition troubles as part of the engine.

 

[Dave Barnett]

Re: Need help with a spark problem

Your post is confusing, Dave. If you have "a" good coil, are really getting "good fire" to both cylinders and measuring it with a meter (!!!) it makes no sense to me that the next sentence says there is no spark.

If we assume that your engine has a dual magneto there should be two coils and two sets of points to serve the two cylinders. Is this the case? If not please tell us what you do have.

I am moving this back to the Other Outboards Forum because we ordinarily consider ignition troubles as part of the engine.

Yes It has two coils and other than being an old jet motor the power head is much the same as any other outboard I've seen. It sure has me scratching my head. I can get an arc using a nail in the plug wire grounding against the block but when I put the plug in I get no arc. I have tried brand new plugs and the old ones that was in the motor when I got it. The old plugs are champion J8C Thanks JB for moving this. Sorry I posted in the wrong spot. I was wondering about that and opted to go with electrical. Thanks again. Dave

 

[Dave Barnett]

Re: Need help with a spark problem

Gonna bump this back up in the hopes someone can figure this out.

 

[CATransplant]

Re: Need help with a spark problem

Yes It has two coils and other than being an old jet motor the power head is much the same as any other outboard I've seen. It sure has me scratching my head. I can get an arc using a nail in the plug wire grounding against the block but when I put the plug in I get no arc. I have tried brand new plugs and the old ones that was in the motor when I got it. The old plugs are champion J8C Thanks JB for moving this. Sorry I posted in the wrong spot. I was wondering about that and opted to go with electrical. Thanks again. Dave

No spark when you ground the threaded part of the plug against the head? But you get spark when you use a nail? that just doesn't make any sense.

Sheesh! Just noticed that this was my 6000th post here. I'm an Admiral! WooHoo!

 

[JasonAych]

Re: Need help with a spark problem

No spark when you ground the threaded part of the plug against the head? But you get spark when you use a nail? that just doesn't make any sense.
!

Unless of course they are those "april fools day" spark plugs

 

[CATransplant]

Re: Need help with a spark problem

Unless of course they are those "april fools day" spark plugs

Or the plug isn't fully inserted in the cap, I suppose.

 

[DECK SWABBER 58]

Re: Need help with a spark problem

I'm gonna take a stab at this.
My expertise is automotive but the principle's are the same.

If you truly have the plug "grounded" (a jumper wire with alligator clip is best)
then the spark is weak. It takes a lot more voltage to jump the plug gap then
with just the plug wire alone. I have never heard of measuring spark with a volt
meter. (Maybe I just learned something)? If you hold the wire without the plug
1/4" from the cyl. head will spark jump this gap?

Think about your car, truck or tractor, etc. The ignition system produces thousands
of volts. but very little amperage. Thats why it doesn't kill you. I think you have
weak spark from the ignition system.