2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

[Tim67580]

Hello All, I have been lurking for quite some time now, but just finally registered today. (I have a problem

I have a 2000 Yamaha 225HP OX-66 SW series II. The complete motor has unknown hours on it, however the powerhead has just under 80 hours. I have been having very (seemingly) minor problems with the motor.

The problem is slightly surging RPMS (100rpm increments or so) at speed. And its not constant or consistent. It will cut back, run for a minute or so, then run fine for 20 minutes or so. I had my mechanic (lifetime Yamaha guy supposedly) check it out. He said he ran every test he could think of on it, and it seems to be dropping cylinder 5 when warm. The only probable cause he could give me was a bad ECM. He did however say that he said he has never seen that before.

Any suggestions or comments?
Anyone know where I can find a new/used ECM at a reasonable price?

Any input would be appreciated. -Tim

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

whats the exact model number? what I am shooting for is to identify if its a 3.1L 225 or a 2.6L 225, memory is fuzzy and for a time they made it both ways.
your surging is most likly going to be fuel related. what method was used in determining #5 dropping? is number 5 dropping spark or fuel? and that is why I also need to know if its a 3.1 or a 2.6. entirely different setups on the 2 engines.
when was the last time the VST and the screen in the pressure regulator was cleaned? when was the last time the spark plug caps were checked? when as the last time the fuel pumps were serviced?
does your tech have at a minimum the yamaha fuel systems and electrical systems certification hanging on the wall? would be even better to find a tech with a yamaha master technician certification on the wall.

 

[Tim67580]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

You have a PM Rodbolt. Thanks!

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

looked at the PM and the link, repost here with the symptoms and the tried solutions so far. this is something I have answered a few times in the past.
but for the sake of others lets keep it here. that and I tend to forget to look at PMs and emails

 

[Tim67580]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

Alright, I will try to post as much information as I can. Please bear with me if it doesn't flow too well as I am trying to piece together a few of my other threads from another message board to make sure and not leave anything out.

The problem is occurring after about 45min to an hour of use. At cruising speeds 3500+ RPMs. It just occasionally will drop RPMs almost like a studder, causing a 2mph change or so while on plane. I am aware of the cylinders cutting off at low/idle speeds, but this is not my case. This is at High RPMS

In the past 20hrs the all the low pressure fuel pumps have been replaced, the VST has been removed, cleaned, and I ***-U-ME the filter was replaced, as well as the O2 sensor being cleaned.

He attempted to swap the coils several times, and the problem remained with the number 5 cylinder leading me to believe it is definitely something electrical.

I spoke with the mechanic one more time today and here is an update:

He said the #5 cylinder looses spark. It is definitely a spark issue. He
said the voltage is too high in the charge coil which means it is not
getting through the ECM.

He checked all the electrical connections as well as pin connectors.

He is going to make a list of the things he has tested and get back to me. Everyone I have talked to has never heard of a Yamaha ECM going bad including my Mechanic.

All the information I have for the motor is as follows:

2000 (Manufactured 9/99) Yamaha 225HP
Model SX225TXRY
Serial # 62J104795

Also, The serial number he gave me for the ECM is:
65J-01F8T33772 (This doesn't seem to match any of the Yamaha part number formats) Also with 9825 on the Casting. Any help would be greatly appreciated. Thanks, Tim

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

buyt an ECM and odds are your gonna have a spare.
what I whish to know is the method of determining loss of coil primary voltage at RPM.
if its a pulser coil then the winky blinky will show it but ONLY at the time and RPM it hapens, that ECU stores NO codes, will only show a code if its active at that moment in time.
the stator overvolt is total BS, if that were true you would lose a bank not just a cylinder, as the 3.1L motors split the High and low speed coils into port and stbd banks.
we did see a few that with heat would gradually lose voltage unitl spark got very erratic.
brings me back to methodology.
is he guessing or can he provide coil primary input voltages while its failing. also wish to see pulser coil voltage for the failing cylinder while its failing.
the ECU is rather stupid, garbage in means garbage out. however the ECU does not do much with pulser or stator voltages other than switch the on and off.
the injectors can be tested with a peak reading meter as well, the specs are not published but with correct training and a stint as an FC in the USN its very simple.
speed is rather meaningless to me, in plain terms it should be against the law to put a speedo on a boat or a fat man.
what kind of RPM loss are we talking.

 

[JUSTINTIME]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

i told you rodbolt would know

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

never said I knew, but I am confident if it was at my shop the diagnois would have been done already.
the ECU is rather stupid, garbage in grbage out, so ya check all the inputs then check the outputs, it the two arnt correct ya got the issue resolved.

 

[Tim67580]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

I am experiencing around a 300rpm drop when it occurs. I am not sure of the method which he has used to diagnose it. I am still waiting to hear back. Thanks, Tim

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

only way to tell is to monitor stator output voltage, should be stable at about 150V above 3000 RPM or so, primary coil voltage will be the same, pulser coil output voltage will be about 30V, fastest way to tell is simply watch the CDI output(ign coil primary) at the problem RPM.if its stable about 150V then ign is ok look at fuel.
the ECU wont record anydata for retrival it will only display a code on the diagnostic test lamp while the failure is active.

 

[Tim67580]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

New hypothesis: Guy swapped ECMs with a similar motor, problem still occurred. Now he says one bank of cylinders is running hotter than the other and causing it to cut out. What could cause this. He is going to check out the impeller etc. Says other probable cause could be the Head Gasket.

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

hahahahaha
good luck.
lucky for you the base powerhead only costs about 4200, you will need it with your current crop of clowns.
however as we know nothing on this board is ok .
tell them if they wish any lessons in trouble shooting, read some good books.

 

[Fishin with buds]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

wow, i saw this forum a few days ago...should have read it sooner.

I have a 225 txrs(1994) 3.1L and have the exact same issue at mid range to high speed, dropping a few hundred(200) RPM and barely fluctuating speed. also, if it cuts out at idle, i cant get it started for th life of me and have been towed back several times. i have a post going on what i have done so far(SEARCH 225txrs) but am really leaning towards a fuel issue as the engine was inspected by a yamaha master tech and everything was fine. so the only thing that changed was going to my sh*t fuel and fuel system.

im getting my new fuel pumps today. at the least, i wont have to worry about those. ill run it this weekend and check back.

good luck.

 

[ghind]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

I'm not your expert, but then your dealer doesn't seem to be either. Does he know what CSS is? When is cylinder 5 shutting down? Is he just testing this at low RPM and finding it isn't firing then?

My bet is that cylinder 5 isn't firing cause he is testing at low RPM and the computer is telling it not to fire (CSS).

This means your problem is something completely different and you only have the same fuel system problems that anybody else runs into. These are reliable motors but when they do have a problem it is usually just the same few things.

How old and how many engine hours on your 3 fuel lift pumps.

When was the VST filter cleaned?

Has the mechanic performed a vaccum test on the fuel system

Rodbolt may chime in with some tests or may suggest you just search.

Firstly, are you SURE your problem is electrical?

 

[Tim67580]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

While this Mechanic may not be the "best" there is, but he is knowledgeable, and He is what I have access to, and I know and trust he isn't "screwing me."
That being said, I will re-iterate the problem.

High speed, High RPM Miss, Occurs at 3000RPM+ and is a drop of about 2 to 300 RPMS. Has been isolated to a spark issue with Cylinder 5 and he has experienced the symptom at speed, both in and out of of the water. The Mechanic tells me one bank of cylinders is running hotter than the other so it is temporarily shutting down cylinder 5 to cool the bank, then when temperature is reduced it regains operation. And that is what he thinks is causing the drop in RPM.

VST, all Fuel pumps , and Filters have been cleaned/inspected/tested/replaced in last 20hrs. The Power head is a Factory new Yamaha unit with just under 80hrs on it.

He tested the running temps and says the Cylinder bank with the #5 cylinder is running hotter than the other bank, and the computer is telling it to shut down. He has tested and inspected the temp sensors and thermostats, and is going to check for impeller, HG leaks, etc.

All of my knowledge is with car engines, however It seems to me that there could only be a handful of things that could cause heating/cooling issues with a motor.

If anyone has any input It would be greatly appreciated. Specifically What could cause One bank of cylinders to run hotter than the other? Also, the engine is not "Over Heating" and I am experiencing no warning sounds. Thanks, Tim

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

and I will reieterate.
your tech is clueless.
there is nothing on the engine that will shut down cyl 5 with any temps.
and I will restate, you have to check ign coil primary voltage with a peak reading meter at the problem RPM.
so you can check the systems as per the manual and my previous posts or you may get to post about burned pistons.
cause if it isnt ign its fuel, guess what and how the piston is lubricated ?

 

[keesload]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

Rodbolt & Tim67580,

I am deffinately not an expert but I do have a SX225txsr and experienced a similar problem when I first purchased the motor used. I believe rodbolts assesment of it being a fuel issue is probably correct. If you pull the electric fuel pump out of the cannister you will find a fine mesh screen filter. I bet it is not clean. A lack of fuel & oil to cylinder 5 would explain the higher heat in that cylinder bank and explain the rpm drop. Even before cleaning the screen all the pressure tests from the fuel pump seemed within yamaha tollerance approx 36lbs. Thus the issue only showed at higher rpm's. The heat issue was not great enough to cause the motor to idle back in safe mode but it was slightly higher. After cleaning the screen filter and putting it back together the cylinder drop and the heat issue went away.
Rodbolt, please let me know what you think about this solution.

 

[rodbolt]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

3.1L CCS,Controled Combustion System.
at startup and warmup all 6 fire, after normal idle is obtained #2 does not fire above 800 RPM to 2000 RPM and number five is shut off between 600 RPM and 2000 RPM.
to many techs trouble shoot the design feature.
we did see a few stator issues but very rare,
usually its either the lift pumps,fuel rail pressure or the inlet screens to the injectors.
however,a faulty or defective/dissconected O2 sensor can fix fuel rich at low speed and lean above 4000 RPM, DO NOT RUN above 40000 if O2 sensor is suspect or hasnt been checked for proper output voltage at the correct RPM's as per the tech bullitens.
if the O2 sensor keeps telling the ECU its running rich the ECU will react by shortening the pulse width(leaning the injectors) until a piston pops.
like I say, computers are rather stupid but they usually do as commanded.
sorry if I get jiggy, but this stuff is rather easy most the time but it has to be tested in a systematic approach with a bit of understanding of a speed density EFI setup.

 

[joost]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

Can someone tell me please what caused this problem?
Thank you?

Joost

 

[robert graham]

Re: 2000 Yamaha 0X-66 225hp drops cylinder 5 when hot?

After reading all this, these motors seem complex to me...think I'll stay with my 2 stroke, carbureted, premix motor...seems like a lot less to go wrong and maintain. Hate to sound like a neanderthal, but how many pumps, filters, screens and sensors can a motor have before it gives up something in overall dependability for the sake of performance and fuel economy? Good Luck guys!