Wrong spark plugs? / Spark plugs burned

[JBehrens]

Boat was running rough this last weekend had a hard time getting on plane and wouldn't break 28mph, I thought maybe due to the fact it was 120+ outside and that there was a lot of gear/people in the boat but upon closer inspection it looks like the spark plugs might be apart of the issue. Pulled the plugs and found the #4 plug to be burned, it looks like the dealer also installed the wrong plugs in the boat LFR6A-11 (gapped at 1.1mm) not the LFR6A (.85mm). Has anyone experienced issues with plugs not waring evenly? The #4 is really burnt, makes me thing something else might be happening with that cylinder. Any thoughts?

 

[anmut]

How long have those incorrect plugs been installed? Personally, I'd dump some Seafoam into the cylinders with the plugs out and crank them. Put the old plugs back in, start the motor, and let them burn off the carbon. After all the smoke is gone, put the new, correct, plugs in. Go from there.

 

[AZMark]

How long have those been in there? I’ve never seen plugs so white as those other 3. The brown one looks relatively normal to me for a plug that’s been in there a while.

 

[JBehrens]

Plugs have been in for bout 20 hours give or take, since the beginning of May. I just swapped plugs, was planning on putting a healthy amount of SeaFoam in the fuel on the next fill up

 

[HangOutdoors]

Plugs have been in for bout 20 hours give or take, since the beginning of May. I just swapped plugs, was planning on putting a healthy amount of SeaFoam in the fuel on the next fill up

That is why I wouldn't let a dealer touch my boat, unless absolutely necessary for warranty work.

 

[JBehrens]

That is why I wouldn't let a dealer touch my boat, unless absolutely necessary for warranty work.

This was the first and last time.

 

[212s]

Boat was running rough this last weekend had a hard time getting on plane and wouldn't break 28mph,

Plugs 1-3 look fine, plug 4 looks like carbon build up and/or incomplete combustion. If the gap is too large, the plug won't fire properly and you get fuel carbon build up. The engine will appear to run rough. I would simply install the correct plugs and run it WOT for 10 minutes to clean the cylinders, then pull the plugs to confirm condition. If the 4th plug is still dark, you might have a fuel injector stuck letting in too much fuel.

Have a look at this page which shows plug conditions:

https://ngksparkplugs.com/en/resources/read-spark-plug

This is how my factory installed plugs looked at 201 hours (click to enlarge), the colour and condition is ideal:

 

[JBehrens]

Plugs 1-3 look fine, plug 4 looks like carbon build up and/or incomplete combustion. If the gap is too large, the plug won't fire properly and you get fuel carbon build up. The engine will appear to run rough. I would simply install the correct plugs and run it WOT for 10 minutes to clean the cylinders, then pull the plugs to confirm condition. If the 4th plug is still dark, you might have a fuel injector stuck letting in too much fuel.

Have a look at this page which shows plug conditions:

https://ngksparkplugs.com/en/resources/read-spark-plug

This is how my factory installed plugs looked at 201 hours (click to enlarge), the colour and condition is ideal:

View attachment 204507

>
200 hours?! That looks clean for 200 hours, I recall that last year the #4 looked a little worse then the others so you might be onto something with that. I got new plugs in and plan to put SeaFoam in the tank so hopefully that helps the injectors out. #4 has dry fouling for sure

 

[212s]

>200 hours?! That looks clean for 200 hours

They should look like that no matter how old they are with fuel injected engines - it indicates proper combustion. The only thing wrong with my old plugs is some wear on the electrodes that leads to a widening gap. They were still within spec and clean with minimal insulation wear, so they could probably do another 100 hours, however I changed them as the internal structure wears as well, and you can't see inside the plug, so I erred on the side of caution and swapped them out. After changing them, I hit the same 53mph top speed so my old plugs weren't worn very much. I may run my new plugs to 300 hours before swapping them - I pull them a couple times a year to verify wear and condition so I'll see how the new ones wear and go from there.

I recall that last year the #4 looked a little worse then the others so you might be onto something with that. I got new plugs in and plan to put SeaFoam in the tank so hopefully that helps the injectors out. #4 has dry fouling for sure

Hopefully the injector cleans up. I suggest you pull the new plugs after you run it for 10 hours and check the condition...that will help let you know what's happening in the cylinder.

 

[JBehrens]

They should look like that no matter how old they are with fuel injected engines - it indicates proper combustion. The only thing wrong with my old plugs is some wear on the electrodes that leads to a widening gap. They were still within spec and clean with minimal insulation wear, so they could probably do another 100 hours, however I changed them as the internal structure wears as well, and you can't see inside the plug, so I erred on the side of caution and swapped them out. After changing them, I hit the same 53mph top speed so my old plugs weren't worn very much. I may run my new plugs to 300 hours before swapping them - I pull them a couple times a year to verify wear and condition so I'll see how the new ones wear and go from there.

Hopefully the injector cleans up. I suggest you pull the new plugs after you run it for 10 hours and check the condition...that will help let you know what's happening in the cylinder.

Makes sense. Next trip is Lake Powell so the boat will get a solid 15-30 hours on it. If it is still got carbon buildup, do you think it would be anything but the injector? I'm guessing a new injector might be worth a shot if that is the case. Thanks for all the help!

 

[212s]

Makes sense. Next trip is Lake Powell so the boat will get a solid 15-30 hours on it. If it is still got carbon buildup, do you think it would be anything but the injector? I'm guessing a new injector might be worth a shot if that is the case. Thanks for all the help!

Injector seems most probable, however it could also be a sticking piston ring letting in oil fouling the plug (doubtful since it's dry), or a weak spark from the coil. It could also simply be #4 plug is failing...if the new ones perform well and remain clean, the plug or connection was bad. If it's fouled after your trip, you can swap #3 and #4 coils and see if the fouling follows the coil. First you need to see how the new plugs work...and go from there...

 

[JBehrens]

Ok I think I might have figured out what the issue is. Here is a clip of the boat running rough and how it acts. I ran some tests while out at Lake Powell and discovered that when the boat acts up if I stop and unplug then plug back in the connectors to the spark plug coils the issue would go away for awhile (maybe a day or two) without issue. I repeated this a few times with the same result each time so my guess is there is a bad connector or coil in the mix.

 

[212s]

Ok I think I might have figured out what the issue is. Here is a clip of the boat running rough and how it acts. I ran some tests while out at Lake Powell and discovered that when the boat acts up if I stop and unplug then plug back in the connectors to the spark plug coils the issue would go away for awhile (maybe a day or two) without issue. I repeated this a few times with the same result each time so my guess is there is a bad connector or coil in the mix.

Clean the contacts thoroughly and try again. If it continues to be an issue, you probably have a weak coil.

What did the plug look like?

 

[JBehrens]

I pulled the plugs the first time it acted up, all 4 looked the same and clean, they might have had 5-8 hours on them at most so hard to tell. I have not pulled them post trip

 

[JBehrens]

Finally had a day to go out and do test/tinkering. Looks like I found the source of the issue, #4 cylinder connector to the ignition coil is bad. The connector and coil look like they have been sitting at the bottom of the ocean. Anyone know of where to get the connector?

 

[FSH 210 Sport]

Finally had a day to go out and do test/tinkering. Looks like I found the source of the issue, #4 cylinder connector to the ignition coil is bad. The connector and coil look like they have been sitting at the bottom of the ocean. Anyone know of where to get the connector?

View attachment 211319View attachment 211320

I would think you can get a loom repair kit for that plug…have you tried checking with the Yamaha parts dept?

 

[Judge]

Finally had a day to go out and do test/tinkering. Looks like I found the source of the issue, #4 cylinder connector to the ignition coil is bad. The connector and coil look like they have been sitting at the bottom of the ocean. Anyone know of where to get the connector?

View attachment 211319View attachment 211320

Mouser is great! https://www.mouser.com/c/connectors/

They stock connectors and pins for every major connector used in automobile and power sports. I have had great success finding the connector housings and pins to make my own accessory cables to plug into factory connectors on snowmobiles, etc.

The connector in your picture is possibly a TE Connectivity connector.

This website is good for trying to match it by picture.... Connectors - 3 Cavities

 

[JBehrens]

I would think you can get a loom repair kit for that plug…have you tried checking with the Yamaha parts dept?

I have not looked for that, I didn't know there would be a rebuild kit for these.

Mouser is great! https://www.mouser.com/c/connectors/

They stock connectors and pins for every major connector used in automobile and power sports. I have had great success finding the connector housings and pins to make my own accessory cables to plug into factory connectors on snowmobiles, etc.

The connector in your picture is possibly a TE Connectivity connector.

This website is good for trying to match it by picture.... Connectors - 3 Cavities

This is great, going to be fun to try and find the right one but I image they have it

 

[David Martin]

Been there seen it ...............plug is running rich...most times it a dirty/corrosion inside the fuel injector....... not getting a good spray. I cleaned my injectors and replaced the filter screens that are in the injector...........simple job with the right tools. On cars I would just replace the injectors 25 to 100 dollars but as most things in the marine world and the Yamaha injectors were around 200 bucks each and above...........hence the reason I took the time to clean and purchase a few tools.....like an injector pulsar(ebay and a filter screen remover tool. Some of the spray patterns I got on the pulsar were vary ugly at best, and was almost a full on piss stream on a few of the injectors.

This was also verified on my oil analyses...... the oil had high gas content. The cylinder walls also suffer when you wash the down with too much unburnt fuel..........not good in the long haul.

PS I ran injector cleaner for several tank fills and the only thing it cleaned out was my wallet.

 

[FSH 210 Sport]

Been there seen it ...............plug is running rich...most times it a dirty/corrosion inside the fuel injector....... not getting a good spray. I cleaned my injectors and replaced the filter screens that are in the injector...........simple job with the right tools. On cars I would just replace the injectors 25 to 100 dollars but as most things in the marine world and the Yamaha injectors were around 200 bucks each and above...........hence the reason I took the time to clean and purchase a few tools.....like an injector pulsar(ebay and a filter screen remover tool. Some of the spray patterns I got on the pulsar were vary ugly at best, and was almost a full on piss stream on a few of the injectors.

This was also verified on my oil analyses...... the oil had high gas content. The cylinder walls also suffer when you wash the down with too much unburnt fuel..........not good in the long haul.

PS I ran injector cleaner for several tank fills and the only thing it cleaned out was my wallet.

I think you may have missed post #15 above…