Maybe the dumbest Question ever asked...

When I pulled the plugs on my 1985 Force 85 hp O/B I was surprised to see the plugs have no electrode, they are just flat at the firing end. Why is this? I've never seen or heard of this type of plug before. Explanation please. Thanks. Just may be the dumbest question ever asked here but I don't know so I ask.

Re: Maybe the dumbest Question ever asked...

That is strange isn't it? I have an 89 force 125 hp and my plugs are same way. They discharge spark to the side. Must be for clearance so as not to hit piston on top stroke. It works in my motor just fine and yes they come that way.

Re: Maybe the dumbest Question ever asked...

These are called surface gap plugs and are used on electronic ignitions. They require the very high voltage delivered by electronic ignition to fire and usually will not spark with magneto ignition or points and coil battery ignition, especially at cranking speeds. They do tend to foul easier and if you start having problems with starting or idle, remove and clean the plugs before trying anything else.

Since the center electrode is completely surrounded by the plug shell, they are not exposed to combustion heat and are cooled by the shell itself. Because of this, the plugs are "dead" cold. This type plug is used in some outboards to prevent pre-ignition and detonation. Do NOT use a regular bent electrode plug in your engine.

Re: Maybe the dumbest Question ever asked...

Cool, thanks for the information. I've just never seen or heard of such a thing,(guess we learn something new every day). I guess I'll need to get these plugs from a marine/boat shop, or can these plugs be found anywhere regular plugs are sold? Thanks for explanation.

Re: Maybe the dumbest Question ever asked...

Frank Acampora said:

These are called surface gap plugs and are used on electronic ignitions. They require the very high voltage delivered by electronic ignition to fire and usually will not spark with magneto ignition or points and coil battery ignition, especially at cranking speeds. They do tend to foul easier and if you start having problems with starting or idle, remove and clean the plugs before trying anything else.

Since the center electrode is completely surrounded by the plug shell, they are not exposed to combustion heat and are cooled by the shell itself. Because of this, the plugs are "dead" cold. This type plug is used in some outboards to prevent pre-ignition and detonation. Do NOT use a regular bent electrode plug in your engine.

Click to expand...

That explains it.

When getting my 55 Chrysler running. I thought of changing the plugs. The old ones didn't look bag, but you never know. After about 5 minutes at Napa, they gave me the "flat" plugs.

Put them in the motor and ran like crap.
Put the old ones back in and it works good.

Re: Maybe the dumbest Question ever asked...

Hey buzz: My second boat was a 1969 14 foot Glastron with a 1967 55 Chrysler. Sweet little hull and I wish I still had her.

Re: Maybe the dumbest Question ever asked...

Any auto parts store should sell them. Advanced auto parts sold them for under $5 a piece. I got NGK and they work great, but thats a whole other debate.

Tom