98 swsll 225 plug fouling

[retiredalaskan]

I have a sws 225 that fouls the #4 plug to the point that it completely covered when i idle a lot while *****ing,other plugs are not to bad a little rich on oil i've checked linkish to pump it's ok any help as to were to look would be great thanks ****..

[Ken]

****,
Sounds to me like you are not getting proper spark to cylinder 4 at low speed. I would try new spark plug wire/s and maybe a new coil - or just swap wire and coil from another cylinder and see if the symptom follows.
Good luck [img]smile.gif[/img] ,
Ken K

[retiredalaskan]

thanks ken but i was under the impression that # 4 plug was shut off when under 3k rpm is that not correct . thanks ****

[Ken]

****,
There are some Yamaha V-6 engines that do exactly that - which ones and which cylinders, I am not sure. Which brings up an interesting point:
if the spark is not there and the cylinder is still getting a "charge" of gas/oil laden air, how in the heck do the plugs not foul out on all of those models all the time ?
I am showing my ignorance here - but, hey, this is how you learn this stuff [img]smile.gif[/img] ! I am hoping someone with more knowledge than me will step up to the plate here and explain why Yamaha "shuts down", I think it's two cylinders, at low speed on some of their model V-6s. How in the heck can this be of any advantage, and how do you keep the plugs from fouling out ?
Ken K

[retiredalaskan]

after having a good nite's sleep,I checked my coils they were all right 3.2k ohms,but the plug caps were not 3 were 5k ohms,1 was 175k ohms 2 were 60+k ohms,guess which one was 175k?? well of course it was #4, I'll try to pick up some new ones monday but i'm pretty sure this will fix it.anybody have any other ideas?? thanks ****

[boats.net]

I think you are on the right track with the plug caps, I do see that a lot. It's #2 and #5 cylinders that drop off at idle on that engine so #4 should be firing at all times. Ken we don't have any problems with the plugs fouling out on #2 and #5 compared to the rest of the cylinders. On the fuel injection models the ECU controls the injectors as well as ignition, the books doesn't say that the injectors misfire at idle but it is possible.

[Ken]

boats.net,
Thanks - it is amazing to me that the motor runs so well with two cylinders out of six not firing at idle.
Ken K [img]smile.gif[/img]

[boats.net]

Ken
Actually they do run smooth but they dont sound quite right compared to most Yamaha V6 engines, it makes me want to do something for it. But Yamaha wants to make run smooth at idle and they do that.

[retiredalaskan]

thanks boats .net ,I have already ordered replacement ones from you should have rhem this week thanks ****..

[retiredalaskan]

boats .net I forgot to ask you why does yamaha use a resistor plug cap instead of a plug that can be changed out when you change plugs??what would happen if you eliminated the resistor in hte cap??? thanks ****

[Ken]

****,
Be sure and post your results so that we all can learn from your experience [img]smile.gif[/img] .
Good luck,
Ken K

[boats.net]

Yamaha uses resistor plugs and cap to reduce any magnetic field around ECU and some models the injector drivers, the ECU is very senitive and I havn't seen much of a problem with the newer models but with the old V6 Excell if you put nonresistor plugs in it the timming would go nuts and jump all over the place.