9.9 1990, rude plugs to hot?

[rasteele]

Is to hot a plug a bad thing, this motor starts on first pull but after running to the first fishing spot, about 5 minutes, it don't want to start very well. New carb kit, the actual right main jet now, New plastic top, new lines, new fuel. Could a too hot of a plug cause this issue, pre ignition?

 

[boobie]

It could. What plugs do you have in it ??

 

[175se]

Just finished one, idle tube was hindering movement of the float. Would start then couldn't restart. just more input.

 

[rasteele]

I haven't been able to check the plugs yet and I put new kit in yesterday along with the new idle hose but haven't tested it. That could have been the problem. I'll post back Sunday after going out

 

[Vic.S]

I haven't been able to check the plugs yet and I put new kit in yesterday along with the new idle hose but haven't tested it. That could have been the problem. I'll post back Sunday after going out

The plugs should be Champion QL77JC4 or QL82C gapped at 0.030"

 

[racerone]

Rasteele, what do you understand about " too hot " a sparkplug ?------Hotter sparkplugs have a longer path for heat to travel away from the tip.-----Thus they are hotter when running.----It has nothing to do with " hotter spark " on them when cold.

 

[rasteele]

I had read somewhere that to hot a plug could cause pre ignition. But your right I had no idea what(hot) actually means

 

[rasteele]

They are br6hs nkg

 

[Vic.S]

BR6HS are resistor plugs .... thats what the R stands for, and a NGK heat rate 6 is hotter than QL77JC4

Champion Q series plugs are inductively suppressed

The NGK equivalent of QL77JC4 is BZ7HS ( or BZ7HS-10) The "Z" indicates that they are inductively suppressed and a 7 is a grade cooler than a 6.

The unsuppressed B7HS (or B7HS-10) will also be suitable but you are likely to have problems if you continue to use the "R" plugs


You will be told that only Champions are suitable but that is because NGK "R" plugs are often sold, even listed, as equivalents of Q series plugs. They are not!

I have no problems with using NGK of the correct type ( I have a set for my 6 hp Evinrude) because outside the USA the rest of the world regards NGK plugs as far better than than Champions


So Use QL77JC4, QL82C, BZ7HS or B7HS but NOT BR6(or 7)HS plugs .


BTW -10 added to an NGK number indicates that they are supplied ready gapped at 1.0 mm ( 0.040")

 

[rasteele]

Hey Vic, imma go tonight and get plugs you recommend, but just curious, what exactly is the difference of the resister plug compared to the champions and also, when I gave the AutoZone the part number he said these were the aftermarket or equivalent as same plug

 

[rasteele]

Man, plugs really make that big a difference in performance? I thought you had spark, you were good. Learning a lot here, thanks guys

 

[Vic.S]

Hey Vic, imma go tonight and get plugs you recommend, but just curious, what exactly is the difference of the resister plug compared to the champions and also, when I gave the AutoZone the part number he said these were the aftermarket or equivalent as same plug

They are difference forms of interference suppression. The standard method is by incorporating a resistance into the plug,. typically around 3 to 5 kohm
This is not suitable for some CDI ignition systems and a coil or inductance with a lower resistance ( about 40 ohms i believe) is used

I believe the Champion Q series plugs may have been specially developed for use with OMC CDI systems.

You have discovered what i said earlier, namely that the NGK resistor plugs are often sold as equivalents of the Champion Q plugs.

I believe the NGK Z type are a relatively recent addition to the NGK range. They are equivalent to the Champion Q plugs.

If in doubt always stick with the manufacturers recommendations, in this case QL77JC4 or QL82C.