01 200hpdi won't idle in water

[21contender]

Have done multiple searches and found nothing related to my condition. Any thoughts or suggestions greatly appreciated.
2001 200hpdi 250hrs, compression 115 to 120 on all 6 cylinders, new VST strainer (very little trash found in bottom of canister) new steel can EFI filter,new filter in clear resevoir bowl, new oil tank filter, new water seperator, (fuel sample revealed no water and minimal trash in seperator). 52psi with key on 48psi engine idling on trailer for low pressure fuel system.
Condition: engine cranks and idles fine on trailer, accelerates in neutral fine on trailer. When engine is put in the water it won't idle. When at the landing with boat on trailer if you trim the engine up enough to have the foot in the water but the prop out of the water engine will crank up and idle fine, as soon as you trim the engine down and begin to submerge the prop engine cuts off. If you throttle it up in neutral it is still difficult to start but it will start and stay running (roughly) only if throttle is up while prop is submerged. If you can keep it running and then engage the foot the boat will pull fine without any skipping or sputtering.
After replaceing the above mentioned parts along with cleaning the plugs that only have 1.5 hours on them. The problem still exists.
Took it to the Yamaha dealer and gave them a detailed description of what engine was doing. 3 days later they called and said it was ready, when asked what was done to address the issue they stated: new plugs, throttle sync, tps adjustment, cleaned grounds, cleaned and tested o2 sensor and water tested in tank for at least half hour.They also stated that ECU was giving a code for internal memory fault and that engine would show no past run data but that this would not affect driveability, thay said that ECU shows current run data but would not retain past data. Picked the boat up went straight to the landing and exact same condition as before.
Now dealer suspects ECU as the problem.
Typically with a back pressure issue I would suspect low compression but 2 different gauges were used and only 5psi variation between gauges noticed
Stumped in Charleston
Glenn

 

[rodbolt]

Re: 01 200hpdi won't idle in water

sounds like you could have carbon blocking the idle relief passages.
remember in N this motor drops two cylinders and above about 1500 drops 2 more.
and if the ECU is nutty yes it could be failing.
whats funny is I have had people telling me they can rev it to 4000 RPM in N on 2 cylinders.
above about 1500 RPM the O2 sensor is not used for fuel corrections.
what is the high pressure rail running?
remember this is an air pump,if you cant get air out you cant get air in.
before I went to bonkers I would test the injector voltage on each injector and test the nuetral switch on the shift slide as well as the shift cut switch.
I would also test the secondary firing voltage of all 6 cylinders in gear both in and out of the water.
you can remove the prop for testing as a safty measure.
when I say secondary voltage I do not mean CDI output.
use a Kv tester and actually monitor the voltage required to make a spark.
have the plug caps been tested?

 

[21contender]

Re: 01 200hpdi won't idle in water

Just an update the boat is still at the dealer. They have had 4 other Yamaha Techs from other dealers come buy to assit in the diagnosis and still don't have an answer. I am asking all the right questions as far as psi's in and out of water, sensors settings and so forth and am getting no real answers.
I'll post the fix when it's done.

I have been a certified Lexus Master Technician as well as a certified Toyota Master Tech for 25years and now own my own Independent Exclusivey Lexus/Toyota Repair Shop so i know how this procedure should be handled. I feel if i had the Yamaha Software for the laptop I could handle this on my own. I didn't realize it would turn into this.

 

[rodbolt]

Re: 01 200hpdi won't idle in water

for a mere 350 dollars you can buy the software.
and still struggle.
99% of the time the laptop simply keeps me from chasing ghosts.
if I brought you a lexus with a potato shoved up the tail pipe would your laptop tell you a tater was up the pipe? I think not.
however if you understand what its telling you you may catch it.
if the ECU sees no issues with any monitored sensor that usually means its not a sensor issue.
compression on a two stroke wont change even if you cap off the exhaust.
are any of these techs Yamaha master techs?
use the dealer locator function and find a dealer with a master tech,or at least look on the dealership wall for techs with both fuel and electrical systems training.
its a very simple direct injected transistor controlled ign system.
not particularly high tech.

 

[21contender]

Re: 01 200hpdi won't idle in water

After approximately 1 month later and multiple phone calls from the service manager and general manager and a visit from an Yamaha Tech REP. De-carboning the engine seems to have fixxed the no idle in water condition. Boat has been in the water twice since picking up and all is fine.
Thanks for insight and information given.
Glenn

 

[99yam40]

Re: 01 200hpdi won't idle in water

sounds like you could have carbon blocking the idle relief passages.

Seems like Rodbolt hit it on the head again.

 

[cousinabe]

Re: 01 200hpdi won't idle in water

Seems like Rodbolt hit it on the head again.

Wonder if he's any good at lottery numbers?

 

[rodbolt]

Re: 01 200hpdi won't idle in water

if I was I would not be posting, I would own an island in the carribean and hanging.

with moderate diagnostic tools and an understanding of what its doing and why, its all easy.