In Flight

[QUINAULTRACING]

On a PRO engine can a coil that starts going bad while racing cause the crisp corners to melt off the ground of a spark plug? Steve August

[propnuts]

I don't have a clue

But I see enough Pro engine guys lurking around here that you ought to get a bump and some kind of response.

[raceright]

something else

I would think it would be something else,grounds can get hot when they are loose.
What engine,stock mag ignition or electronic.

Pat

[PETEG]

doesn't matter, Pat, what kind of ignition. bad coil is not going to melt anything. Will only cause a high rpm miss and drop a few hundred rpm, maybe more than a few. Melting only will occur if timing is too far advanced or jets are too small on a PRO motor. Excessive timing advance usually leaves pock marks in the top of the piston.

[pro350hydro]

Great Answer!

doesn't matter, Pat, what kind of ignition. bad coil is not going to melt anything. Will only cause a high rpm miss and drop a few hundred rpm, maybe more than a few. Melting only will occur if timing is too far advanced or jets are too small on a PRO motor. Excessive timing advance usually leaves pock marks in the top of the piston.

Exactly. I could not have said it any better.

You may double check your timing, maybe back it out a bit. Or jet up a bit. Sounds like it may be on the edge... Is this happening on both cylinders or just one? Also, What carbs are you running? And do you have Power Jets or Dial-a-jets?

[raceright]

My mistake ,thought he was talking about an external not internal problem.
Well at least he got some more suggestions

Pat

[Rex Hall]

Spark plug ground

When the edges or tip of the spark plug ground starts to melt, it is caused by heat, this could be too high timing, too lean carburetor jets, or too big of a prop that is lugging the engine and causing detonation from heat. A lot of motors are siezed because of running too much prop and pulling the pipe up to soon, putting more heat into the cylinders.

[QUINAULTRACING]

Thank you very much

Thank you all very much. This is my first year working on a pro engine. The problem. Too big of a prop, intermittent coil that I thought was a cylinder too rich. So I leaned it out more. Came back in with the crisp corners burned off of plug. Put a bigger jet and new plug back in on that side. Sent it back out. When i saw by the last lap a gas and oil rig was going to pass the boat that I had not fixed anything. Almost did not make it back to shore. Found oil all over the pipe and back of engine and a ice cold pipe. Oh hell this is easy, you have a bad coil I said to myself as I pondered this could have been a lot worst all we had to do was order a new coil. Rex this is the Tim Small engine I bought from you a year ago for Doug Reed. Thanks Again Steve August

[pro350hydro]

Did you check to see if there is a hole on the top of the piston??? Metal on the plug?

[QUINAULTRACING]

No

Did you ever get that VRP shipped to Lee Tietze? Steve

[pro350hydro]

Did you ever get that VRP shipped to Lee Tietze? Steve

Funny you ask. Boxing it up now.

[Rex Hall]

Pro motors

I never heard what RPM the 250 motor was turning before it loaded up? I am not saying that it could not be a coil, but in 6 years, I have only sold 2 or 3, and they were for 125 motors. If you are not turning over 13000 RPM, the setup, prop, or jetting is not correct, or a combination of all of the above. These motors will run at 12400 to 12800, but will tend to sieze or foul the plugs easier because they are under a lot more load if the prop is too big.