OX66 250hp cranking but not starting.

[RickoVenter]

i Guys,

I'm in some serious need of professional help with regards to my OX66 outboard.

First off, I'm based in South-Africa and the OX66 was not sold by Yamaha SA - so they refuse to have a look at the motor. This motor was built by a local guy that traded me for my blown HPDI 250 powerhead(this seemed like a good idea as there are quite a few people who feel that the OX66 was the best 2-stroke yamaha ever built and I obviously don't want to be caught with another blown powerhead). With this said, I cannot tell you which year model the motor is - but rather give you a list of parts with their part numbers that's currently on the motor.

So let me explain the problem that I'm experiencing:
Motor starts fine at home and I idle it for a few seconds and then I have to switch it off as I don't have water running through it, so I'd rather be safe.
Depending on the day, when I get to the dam the motor will at least start and I can drive around (stopping and starting) for a good few hours and then will just not start again. Then there are those other days where I get to the dam and the motor will start with the boat being launched and then after idling for a few minutes (which I normally do to warm the motor up) it just dies and will not come back to life again.

From what I can tell there's no spark, I removed one of the plugs (re-attached the lead) and held it against a clean shiny bolt on the cylinder head while cranking the motor.

Things that I've checked or had checked:
-Injectors
-Fuel Pressure
-Swapped CDIs with someone that's also running an OX66.
-Different Cranking Batteries.
-Atmospheric Pressure sensor.
-Intake Air Temperature sensor.
-Throttle position sensor.
-Charge Coil Voltage.
-Compression Test.
-Replaced VST.
-Serviced the 3 LP-fuel pumps
-Replaced Fuel Pump Regulator/Resistor.

I think the main culprit here is the Pulser coil, but I don't have a Peak Voltage meter to test this. I have ordered a new Pulser coil and will take a few weeks to get here.


So any ideas or pointers on how to find this problem will be highly appreciated.

[99yam40]

should have ordered a DVA adapter to use with your regular meter so you can test things.

Lots easier to test things than guessing what is a problem and what is not

[Bilge Rat]

Get a real spark tester.
Verify you have fuel to motor, squeeze bulb when motor fails and check fuel pressure.

[rodbolt17]

splattergunning.
about the only sport I don't do or reload for.

lets look at that list of worthless stuff you did so far.
most of it would have NO bearing on wheteher it would start or not.

rail pressure must be about 35-38 PSI.

injectors must be clean.

from there I think your all wet with a pulser coil.
there are 6 of them and it will throw a code if they fail.
however some,not all, V6 Yamaha CDI ign pulser coils use a common ground.

lets think a bit.
WHAT components PRODUCE spark and what components CONTROL spark?

google home made spark tester.

charge coils,pulser coils,flywheel magnents and ign coils produce spark.
the TPS,CPS, and CTS control spark.
A digital multimeter with a DVA adapter and some paperclips can test about anything on that motor.

a digital meter could have also tested that resistor and the meter with the DVA adapter is cheaper than that resistor.

[madharchod]

you have a cooked motor now you can invest all your money in it it will never run try and get yourself a new powerhead
cheers

[RickoVenter]

The reason why some of the items are on the list is because the motor was at some of our local "outboard Spe******ts" and these were items which they had me believe were the problem so they replaced them. Only for me to get the boat back still with the same issue and a whole lot poorer.

If I had to explain the whole Event history vs timeline my original post would be a few pages long. Based on my experience over the past year I've realized that I would have to learn about motors and try get to the issue myself. This decision was made 2 months ago so please bare with me.

I admit that the I've tested the Fuel resistor but I did not get close to .55 ohms. Could it be that my meter doesn't supply enough current?

Next few steps would be:
-Get DVA adapter
-Get Diagnostic Indicator (Does part YB-06795 work on all OX66s ?)
-test CTS and CPS (I assume if any of the components involved in con*****ing spark fails - it will cause the ecu to "drop" spark?)
-I'm ignoring ign coils as there's no spark on any of the Sparkplug leads.

Tested already:
-ChargeCoil voltage > 80v when cranking.
-TPS at .5v when Throttle valve fully closed.

Few questions:
-How do I eliminate the Control Harness?
-Under which conditions will the CDI drop spark?
-Oil level sensor or Shift cutoff switch maybe?
-Does the OX66 cdi give spark to all 6 cylinders when cranking?
-Why did Q20 not fix all my issues ;-)

[rodbolt17]

only gets fixed at Q21.

the CDI wont drop spark on all 6 for any reason.
it will drop spark on cyl #5 below 800 RPM and above 600 RPM.
sparks all 6 at cranking speed and below 600.
between about 800 and about 1800 it drops spark on 2 and 5.

the shift interrupt only works when comeing OUT of any ingear position and will cause the engine to misfire briefly.
if you disconnect it the system will work normally but may be very hard to shift OUT of an ingear position with the engine running.

the rest of the sensors WILL NOT cause a loss of spark. period.

a shorted stop switch WILL cause a loss of spark.
to test pull the stop lanyard and crank the motor, if an alarm sounds the system is normal.
if NO alarm then fix the alarm and retest.

lose a charge coil and you lose one bank.

lose the pulser coil ground and you lose all 6.

if you lost spark on all 6, quit chasing sensors.

[RickoVenter]

Just to conclude,

Issue was the Stator(charge coils).

So yes, if I had a DVA adapter it would have made my life so much easier! But seeing that I cannot find anyone in SA selling these and the cost of buying/shipping one is more than Buying/shipping a good working stator from ebay - I've decided to check the difference in voltage(without a DVA adapter) between the 2 charge coils and found that the readings weren't even remotely close to each other. (In my mind they should function similar)

eBay stator installed and motor now - runs and fires up like a dream ;-)

Thanks for all the help in making me understanding this motor a bit better.

[99yam40]

there are places online to find out how to make a DVA adapter, the capacitor was the hardest part to find for me