Burning Spark plug 225

[Barema Bullet]

I have a high speed landing craft with twin 225 yamies on her.
Total hr 950, and we have just started to burn our spark plugs, run time on new spark plug have gone from 200hr regular service to 60hr, any thoughts to why this is occurring?

[bajakeith]

plugs

UMMM,, what do you mean by "burning" ??..if ,ashly white,, your lean..if black you running rich or late timing...if black and oily, you have oil control problem..if very clean you have water leaking into the cylinder...BTW what motor and year ????????

[Barema Bullet]

plugs

Bajakeith,
the engine are yamaha FL225AET & F225AET 2010 models.
Burning spark plugs in the sense that during operation at say 4300rpm, we try to increase rpm but doing this causes the engine to loss rpm (dropping to 3900rpm and jumping back to 4300 and so on until we bring rpm or throttle back to 4300 potion) of the spark plugs are not holding RPM. Once we change spark plugs this issue is eliminated and we can hit 5500rpm no drama.
Black and brown is the color of plugs. Oil issue may be the reason, we also have oil residue on the intake manifolds after intake silencer. This would give reason to spark plug performance right?

[madharchod]

i will be taking the injectors for service as if anyone of the injectors are siezed then definitely you will be getting spark plug burn out and also the oil will be seeping back in the body as shown in the picture

[rodbolt17]

that oil is rather normal.
its from the crankcase breather setup.
oil vapors are fed to the airbox to be reburned and then they condense and that's what you get.

plug failure is a symptom of an issue not the issue.
pictures of a failed part would be more helpful than pictures of a normal thing.

[Barema Bullet]

plugs

bajakeith, madharchod & rodvolt17,Many thanks for your feed back this will b a great help.
Rodbolt17, was not aware that the oil build up was a normal occurrence, but i can turn away from this issue know.
Will defiantly look into the injectors on next service.
My service centre suggested the thermostat, since we done so many hour i will change this as well.
cheers
Barema Bullet

[99yam40]

Not sure what a landing craft is or where you are located, but think this is in a place that may have fuel quality issues.

Burning some types of contaminates will put some stuff on plugs that will short the electrodes to ground instead of jumping the gap as it should

Sounds like plugs are fouling to the point that they are not firing properly.
Could be the fuel contaminates, the plugs, plug wires/caps leaking instead of sparking plugs, or something else.
But plugs are not burning up or out.

Years ago I found new plugs that would fail due to internal problems even when 1st installed, but that was 40 years ago in car dealerships I worked in.

I would hope they have got the quality control a lot better now

Running a motor with a problem could cause major problems to the motor.

Sounds like it is surging like a fuel restriction/ starvation, but do not see how changing plugs will make it better unless something else is being done at the same service
How long does it run well before this comes back?

[Barema Bullet]

99yam40,

Thanks for you input.
We are base in Papua New Guinea - Rabaul, our vessel is a 9.70m coastal trader.

I can agree on have poor fuel quality, as we fill unleaded from 44 gallon drums into fuel tank. Before i came on board this was down with no filter system. we are doing this now and has improve the life of our external and internal engine filters.
Yes it does feel like surging and fuel restriction/ starvation when it occur especially when we increase rpm and you really notice the bouncing of the rpm.

My crew did a run today and experience this issue again and we have only done 55hr since we changed the plugs.

Engine have done 979 hr in less than a years work and our normal Operating RPM is 4500.

It has been in the last 300 hr of running that this has occurred prior to this, all good.

cheers
Stephen

[99yam40]

See if you can post pics of the plugs pulled out when problem occurs, fairly sure that is what Rodbolt was asking for.

I would monitor fuel pressures when problem is occurring to make sure it is steady and in spec just to make sure that is not a problem.

With that rig you may have a hard time propping it properly as your load changes from day to day would be my guess. Tough on the motors.
Are the motors oil levels holding up OK and not making oil?

Seems someone posted before about getting a batch of bad plugs in a remote area and had a problem like this. At least that is what they said.
Are all of these plugs coming from a case that you purchased and have on hand as spares?

Does it help to clean them and then reinstall?

[Barema Bullet]

plugs

Yeah, our load does change day to day between 2T -2.5T even hitting 3T @ times and the engine have been work extremely hard cause of this.
Oil get check every day before use and if holding fine.
We have cleaned and reinstalled same plugs to verify if it is just dirty plugs, unfortunately it doesn't help.

Sorry, have attach pic of plugs just removed Yesterday.

[madharchod]

yep that's definitely your injectors ,as i ran a few boats in Fiji islands and we also fill from 44 gallon drums on to the boats but we had water separators just after the pick up from the tank and before the primer bulb and we were draining the separator everyday as there is always water in fuel and being in the tropics make the condensation even worse and if you leave it for a while then you will start having this problem as this condensation reaches the injectors and if the engine is left standing for a while there will be rust forming on the injectors ans fuel flow will start to be restricted and all sorts of problem will occur
iam due in Papua next month before i arrive in Fiji for two months if time permits i can have a look and most probably diagnose and fix your problem

[Barema Bullet]

I did a check on the resistance on the injectors and they showed 16, in the manual it say they should read 14-15.

looked at pulling them out and check them but we have a run tomorrow, so will wait to its return and i have a complete full 2 days to pull injector out and give to the service centre to run a check on them.

Where you stopping over in PNG? We are based Rabaul and at the moment have a active Volcano going off and with the winds turning around flights might not make it into Tokua Airport and if they do they might no go out.

I will defiantly pull the injectors and get them check ASAP.

Thanks to all for your advise and input, i am sure this is not over for me, as it is hard to get good tech help locally.

Am planning on doing a major over haul (rings gaskets timing etc) after we hit 1000 hrs would you recommend this or just do the basic?

[madharchod]

dont worry mate iam located in sydney at the moment but will be going to Fiji on my way will be visiting Papua on my way these motors are a piece of cake for ,me as i have some 42 years of hands on experience in all 2 stroke and vigorous 4 stroke motors especially in bigger motors .i understand your frustration as we have the same thing in Fiji too lack of expertise but help is always at hand if you need one ,just clean the injectors and place new water separators in the line ,you should be OK ,any mechanic shop which does injector service will be able to clean it just tell him to use pulse cleaning as he would have never seen one of these injectors nor would he have cleaned it so do it anyway as in the pacific this is how we do things as we dont rip off people and we dont have a modern workshop where we can do things by the book so we have to do by what we have in the backyard and modify things our style

[Barema Bullet]

Very true Madharchod, We do what we can in the Pacific,
and thanks again all for your input and assistance.

happy & safe boating.