Yamaha Enduro 60hps Burning Up Spark Plugs

[rodbolt17]

look closely, especially the bottom 3 plugs.
see that green deposit? it aint supposed to be there.
a quick Kv test would most likly indicate low Kv on the bottom row.

the top 3 show insulator fouling, there again it will cause low Kv.

what happens when its an insulator fouling issue, the "spark" will travel down the insulator deposits to the plug shell.

may take 2-3 Kv for this to occur VS 5-8 Kv to actually jump the electrode gaps.

can be caused by incorrect octane,incompatible fuel additives,low combustion temps, thermostats missing/open.

can also be caused by NRA.

a Kv tester is cheap and worth more than ****.

[captainhark]

just a thought,, having the same problems with different engines would lead me to first look at what is common between all engines. ( fuel, oil, additives, )
If it is only your new engines, than I would still have to rule out what is common between engines, then start looking at what has been said about checking outputs of the ignition system.

hark

[99yam40]

can also be caused by NRA.

OK I'll bite

What does the National Rifle Association have to do with this problem


Hopefully you have not pulled the stats because of your overheating problems before

[Bonefishr]

I think I got the right answer. I spoke with the Yamaha mechanic in Nassau. What confuses me is that all the motors are doing it. He tinks I don't think I have the right props on the motors. You can't open the motors up to full throttle. If you do they start to miss. You have to back them off a bit. The ideal top end RPM is 4500-5500. They are running at 6000. I've told the guides not to run them that hard but I think they are anyway. I was told that will fry a spark plug not to mention blow a head. We'll see, what do you guys think about that?

[99yam40]

I never heard of over revving causing plug problems.
What say you Rodbolt?

If you get too high of RPM the rev limit would be hit and CDI would limit RPM by dropping a cylinder(I guess that is how it is done), but do not see how that would hurt plugs.

Not sure how under propped you are as the rev limiter is probably just keeping RPM around 6K.

Best to prop to 5500 with normal load

Rodbolt is a Yamaha Master Tech so he knows Yamaha's very well, pay attention to him.
I agree with the deposits causing plugs to short to ground, but I do not understand how over revving would cause deposits and I do not see how anything else could cause the plugs to not spark correctly.

Still think it has to do with what you are burning

[Bonefishr]

I don't put in additives, never have. My fuel is shipped in from Nassau weekly. If they're putting something in it there's nothing I can do. All the other lodges are running the same fuel....and Mercurys....no problem.

It's possible that I have some thermostats stuck open. It's happened before. Like I said, we run in very shallow water. Some sand may be stopping them from closing. On the other hand, when the lower unit water intakes get clogged due to the sand the motors overheat and drop to low idle. Maybe the guide are not keeping them clean enough and waiting until they overheat to clear them. Maybe the excess heat is burning the plugs up.

The Nassau mechanic was insistent not to over diagnose and get carried way. He seemed confident it was probably the props.

[99yam40]

Just keep us informed if you get the final answer, as this is a strange one.

Are you getting different props?

Still want to know what Rod means by NRA

[Bonefishr]

Yeah...me too...what's NRA?

I'm going to try and narrow this down and do a little troubleshooting.

1) The first I'm going to do when the boats get in this evening is check the thermostats on a couple of them. One motor in particular just trashed a set of plugs in two days. I'll check that one first. I remember a couple times in the past the motors got so hot that the thermos were stuck open.

2) Move the inductive hour meter wire wrap off the coil to the plug wire.

3)Run one of the boats at wide open and double check the RPM. If it's over 5500 I'm getting new props. I currently run 13 1/2 x 15. I think I'll loose about 200 RPM per inch of pitch....correct?


4) If that doesn't work I'll buy some of that testing equipment you suggest and check the kv and NRA......as soon I Rod tells us what NRA it is.(; I'd like to ask one more favor. Would someone be kind enough to post a url where I can purchase an RPM/kv meter, google isn't finding much, maybe it's called something else. I can have it shipped to some incoming guests for delivery. Also, is there such thing as a spark plug tester? I'm sure not every plug I've been changing out is bad. It'd be nice to be able to sort through them. I won't have to buy plugs for years.

I'll let you know what the final verdict is.

[99yam40]

back in the middle 70s a shop I worked at had a plug cleaner/tester that sand blasted the plug and tested it with spark voltage even under pressure with compressed air that you could watch the spark as you put pressure on it, but have not seen anything like that for years. But I have not been looking for one either.
would need to get up over a few KV and maybe 8 to 10kv to test it properly.

I do not know if a 1kv megger would test it well enough or not

Have you looked at this site to see if they have something like what you are running to see what prop they ran? Performance Bulletins | Yamaha Outboards

Will have to do some looking for KV meter and get back,
as far as RPM some inductive timing lights have RPM I think. I just hook up a outboard tach temporarily . All the hand held cheapo ones I tried never worked well, too much noise from ignition system screwed them up

Maybe Rod will give a KV meter brand that is good, I have no idea

[rodbolt17]

NRA
No Apperant Reason.

I actually used this acronym is a US navy casualty report on a failure with a CIWS mount.
F*** I dunno, would not fit in the block.

as these engines are non US market I dont know if they even have rev limiters.

typically spark plugs, run at normal combustion temps, are self cleaning.

if your bouncing the rev limiter on a carbed engine, the fuel/oil is still coming, the spark will be misfired.
misfired plugs cool off rapidly with the non burned fuel.


could lead to funky plug fouling.

but fouling you have.
a Kv test would prove what I am saying.

google Kv testers.
cheaper than **** and worth a lot more.

[madharchod]

i have about 40 of these motors in Fiji and no problem what i did encounter a few years a go is the same thing which you are experiencing the plugs will not work after two weeks as i didn't have any hour meter i guessed the days did everything i could and to no avail ,i can bet you million dollars there is nothing wrong with the enduro 60 motor it is the batch of spark plug which had factory manufacturing problem cant be proven as we live so far from where they made so i changed the spark plug from a older motor which was sitting idle to one that was burning the spark plug and bingo problem solved ,what iam trying to say is if you try BR8HS 10 plug from another area and if it works then you know the batch of plugs you got is faulty
these motors are bullet proof ,you dont need technical experts for these motors its the spark plug mate buy new batch from somewhere else

[rodbolt17]

on the above.
I respectfully disagree.
however I dont see plugs made for outside the US market.
maybe they are different.

but in the pictures, the plug porcelians are running cold.

dang I wish I could spell.

[99yam40]

NRA
No Apparent Reason.

No Reason Apparent matches better

typically spark plugs, run at normal combustion temps, are self cleaning.

if your bouncing the rev limiter on a carbed engine, the fuel/oil is still coming, the spark will be misfired.
misfired plugs cool off rapidly with the non burned fuel.

could lead to funky plug fouling.

but fouling you have.

This makes more sense to me than anything else

google Kv testers

Rod do you have a model or name that works well to recommend?

[rodbolt17]

I have two made by snap-on.
I think they are out of production by snap-on now.
a fellow tech has one by precision I think.
I'll ask at work today.
his was about 30 dollars and does RPM as well as Kv.
mine only do Kv.

[Bonefishr]

Madnarchod.....I agree, these motors are bullet proof. They last twice as long as a Mercury. My last batch of motors had nothing wrong with them and compression tested like new after 8 years. I sold them because I had no idea how many hours they had and didn't want to wait until they started giving me problems. I change the impellors and lower unit oil every year, rebuild the carbs, new thermos and fuel pump diaphragms every other year. I've never had one break down. When they run like sh*t you just change the plugs.

Maybe it is a bad batch of plugs. The box I got from iboats lasted longer than the one I just got from the local dealer. I just threw out a set that lasted ONE day this morning. I have a another box arriving on the mailboat today. I hope it's a different batch.

Rodbolt....they do have rev limiters and an idiot light. When the motors overheat they automatically drop to low idle.

I'm going to try this kv thing'um out. The video makes it look simple enough. GTC TA100 Smartach+ Wireless Ignition Analyzer and Tachometer : Amazon.com : Automotive

One of the motors had a thermostat stuck open. Still doesn't explain why the other motors a cooking plugs. I removed the inductive hour meter wire wraps from the coil on all motors. I had a talk with the guides about not running them wide open and keeping the water intakes clear. We'll see.