Yamaha Enduro 60hps Burning Up Spark Plugs

[Bonefishr]

I operate a bonefishing lodge in the Bahamas. I've been running the Enduro 60s for ten years. I just bought 4 new ones, each one has about 150 hours on them. I have no complaints, these motors are bullet proof BUT.....they chew through a new set of NGK BR8HS-10 plugs about every 20 to 30 hours. I've burned up 75-100 plugs this season. There are no signs of unusual wear or deposits and they have good carmelization. I might be able to get by cleaning them up once but that's it. They look new but just lose their fizz. When the boats throttle up in the morning I can tell instantly if the plugs are going bad.

I think burning up that amount of plugs is ridiculous....and costly. My competitors who run Mercs say one set will last the entire season.

Any advice or suggestions?

[99yam40]

you may need to explain a little better about burning up plugs.

When a plug is burned up, I think of it as electrodes burned down.

Sounds like you are having a problem with them fouling/shorting due to carbon or some other residue.

Could be due to type of oil, fuel, or other additive in fuel mix

[Bonefishr]

The plugs are spotless, they look brand new. The electrodes show no wear. They still spark but the spark isn't hot enough to get full combustion. That's what I mean when I say they lose their fizz. I'm using Yamalube oil at 50:1 and the same plugs the mfg recommends. The carbs are set to mfg specs at 1 1/2 turns open. I have a hundreds of plugs that look perfectly fine. When the plugs start to go bad the motors lose power, take a long time to get on plane, and don't reach max RPM. Give me some time and I'll post a pic of some plugs I just changed out this morning.

[bajakeith]

Uummmmm !!!

Say what ?????

[Bonefishr]

Plug pic

I grabbed these at random, they haven't been cleaned.

[99yam40]

plugs do not loose their fizz.

The gap erodes until the gap gets to large, ceramic cracks and spark jumps to ground, or they start leaking voltage to ground through contaminates of some type across the ceramic.

Or maybe the plug caps are leaking to ground.

Salt will cause leakage to ground.
Maybe you just need to clean /wipe things down

[Bonefishr]

I agree, I don't think plugs should lose their "fizz". As a kid we ran plugs until there was nothing left of the electrodes, just kept cleaning them and regapping. Regardless, I can wash those plugs pictured with gas, shine them up with a wire brush, scrape off what little deposits there are, spray them down with carb cleaner and they still won't work. Somehow they got ruined.
The motors themselves are clean enough to eat off of. I sprayed them down with corrosion guard out of the box, rinse them with fresh water everytime they come out of the water, inside and out, and then spray them with WD-40to disperse any water left on the motor after they air dry.
I just had one motor that trashed a set of plugs in about 10 hours. There are three different ground wires attached to the block. I did notice that the ground wires on the motor were about a half turn lose. Maybe that'll solve the problem.
The only other thing I think of is that I installed inductive hour meters on the motor. They run off a small watch battery. You wrap a wire around one of the coils 6-8 wraps. Somehow when the motor is running the wire wrap senses the spark going though the coil and triggers the meter to track runtime. I don't think that's the problem because they were not installed on the old motors and I still burnt up plugs.

[Bonefishr]

The more I think about it the more I think, as you suggested, it's a ground leak. Out of the box most of the nuts and bolts are loose. After the break-in period I had to retorque every nut and bolt on the motors. Some were hand tight and a couple water manifold bolts vibrated out. I found them laying below the motor. I didn't check the grounds. I'll bet they're all loose.

[99yam40]

I myself would not think it is a bad ground that installing a new plug would fix the miss fire

The charge coils generate a voltage that the CDI stores in capacitors and then releases at a time it is signaled to.

The ignition coils boost the voltage signal they get to KV coming out of the plug wires and is referenced to ground at the coil itself.

The plugs are resister plugs from what I see in the pics. Could the resisters be going bad? Never heard of that before

Might measure the new and old plugs from middle electrode to the metal base with a megger set a 500v and 1kV to see what the readings are and if there is a difference showing a leakage to ground.

If you can touch the plug wires and caps with motor running and not get shocked that would fairly well show the caps and wires are not leaking.
But with washing them down inside and out and spraying WD something could be leaking to ground

Do you have a DVA adapter to measure the charge coil voltages and the output of CDI with to make sure they are in spec?
A KV tester would be a good thing to test the output of ignition coils to make sure that voltage is equal and the same with new and old plugs.
I think Lower voltage would indicate partial grounding and not letting voltage build up aas high

[robert graham]

Those plugs look fairly normal to me..... several years ago I started using one of those $15 Harbor Freight Spark Plug Sandblasters and it works great to knock off those carbon deposits...I never buy new plugs for outboards, lawn mowers, chain saws, cars, anything....just sandblast 'em clean and keep running them....maybe check gap now and then. Good Luck!

[Bonefishr]

99yam40....The resistors have to be being burnt up somehow. I don't have any of that testing equipment on the island. Wish I did. I would find it odd that all four new motors would be out of spec. I suppose it's possible. Maybe Yamaha had a bad batch of parts. I can jump the spark across the caps to the plug without getting shocked. I did it to check the spark color yesterday. Looks good, bright white. I'm going to clean and tighten all the grounds up and wipe the plug caps down, inside and out.

[99yam40]

I hope Rodbolt17 will chime in and give some thoughts as I have never heard of this type of problem

You need to order a DVA adapter and regular meter or the special meter needed for reading the peak voltages and the Yamaha service manual for those motors just so you can verify the voltages. Sounds like you will have them for a while and the manual is needed for troubleshooting

[Bonefishr]

It's has to be something stupid easy to solve. It always is. When I bought my first Yamaha 60 I had a problem with it coming off plane and kicking into low idle. I took the head off to check the head gasket. I went so far as to put it back into the box and ship it back to Nassau for repairs and they couldn't figure it out. I eventually figured it out. We run in very skinny water. The water intake ports were clogging with sand causing the motor to overheat and drop to low idle. All my guides carry a piece of wire to clear the intakes, problem solved. I'm hoping in this case it's just the loose ground wires.

[99yam40]

please post what you find

Are you speaking about clearing the tell tail with wire ir the intake screen?

Sounds like something to indicate a problem( alarm) and identify the problem would be beneficial( gauges)

[Bonefishr]

My last post was way off subject. I'd rather not get sidetracked. The point was that the solution to my spark plug problem is probably a simple one.