Delay in accelerating to WOT

[exttremeparadox]

Hello Everyone,

I'm having an issue with my 2003 VX250tlrb OX66. Here is the situation. On the water, when i advance the throttle to full (WOT), it takes almost five seconds for the motor to engage to WOT. It's like initially no fuel then all fuel. It has been this way for some time and i have just been dealing with it but now there is a new problem with it. The new problem is when i advance to WOT, the boat plows water like its going to take off but doesn't. So, i throttle back to idle and try again. This time it takes the 5 seconds and we are up on plane. Let me list what i have changed on the motor:
- New Chris Carson Carbon Fiber Reeds (this problem was there with the old metal reeds)
- VST Filter
- Fuel Strainer
- All three fuel pumps
- Both thermostats
- Poppet Valve
- Spark Plugs
- Throttle Position Sensor check was good
- Fuel Pressure check was good
- Throttle Valves adjustment was checked and good

The motor has a rough idle and the RPMs vary from 300 to 800 (should be around 730) but I'm always told that it's because its a 2 stroke. I haven't had the fuel injectors cleaned but I'm struggling at how that could be the problem....

Thank you all in advance for any help you can give me,

Chris
2003 Stratos 21XL Magnum
2003 VX250tlrb OX66
8 inch Manual Jack Plate 4.5 inches below pad
25 pitch Yamaha prop
Boat will do 67mph full fuel, full load tow people

[201pro]

The injectors will cause rough idle and low performance. 2 strokes run best when the fuel/air mix is correct and if it is over fueling, it will run poor. The injectors that need reset are normally overfueling.

You listed checking everything except the O2sensor. O2 sensor will give performance issues and rough idle. I would suggest you replace it with the NTK21006. Cleaning doesn’t work well. But will need to clean the housing and dogbone tube.
You will need to change the engine connectors or just solder the new one into the old harness. Search the forum for this replacement and modifications.

[exttremeparadox]

201pro,
Just wanted to give you an update on my issue. I cleaned the injectors and the spray pattern was beautiful. However, when i removed the O2 sensor and looked in the housing, it was blocked by carbon. I removed the housing and cleaned with a shotgun cleaning kit (fit perfect). I ordered the NTK21006 and spliced it in. I will be testing tomorrow to see how she runs. I might replace the spark plugs as I'm sure they are fouled from the work of the O2 sensor. More to come....

[skeeterBill200]

Can anyone point me in the right direction on what wire adapter is used to permanent splice wire to engine for the NTK 21006 O2 sensor? None of the auto parts stores can find this part.

[BuzzB8]

http://www.bbcboards.net/showthread.php?t=1083960

From September, by headhigh.

[skeeterBill200]

Thanks BuzzB8! I don`t know what happened to the stickies but all those great pictures along with the write ups has disappeared. And I`m better with pictures than reading instructions lol

[BuzzB8]

There are a couple pictures in the link I posted. They show how he wired and routed the connection. I suggest taking a picture of those with your cell phone and showing them to the auto parts folks. They should have something similar.

If you click on the first link in the thread, there is more data. Brian found it on eBay. Its for a camaro/corvette LT1 and it's the o2 extension. $10.99.

[Ranger519VS]

201pro,
Just wanted to give you an update on my issue. I cleaned the injectors and the spray pattern was beautiful. However, when i removed the O2 sensor and looked in the housing, it was blocked by carbon. I removed the housing and cleaned with a shotgun cleaning kit (fit perfect). I ordered the NTK21006 and spliced it in. I will be testing tomorrow to see how she runs. I might replace the spark plugs as I'm sure they are fouled from the work of the O2 sensor. More to come....

You cleaned the injectors yourself? Or did you send them off to a service that cleaned, tested, and calibrated the injectors?

[wcs69rat]

Google LS1 O2 sensor connector / pigtail. I know Summit and Jeg's has them and probably numerous other places.

[skeeterBill200]

Ok so I got everything in to replace O2 sensor spliced the wires with the wire harness assembly and I cleaned everything in seafoam only thing I will need to buy another gasket for the chamber to block wall to seal tube sniffer. Some posts suggest there is a metal o-ring and a rubber o-ring and I didn`t see either. Also I cannot find a thin wall O2 sensor socket at the Auto Zone parts store only heavy wall socket available. I removed the sensor in a vice after removing the chamber from engine. Guess I`ll replace it the same way. It looks like this should be torqued in the same manner as an 18mm spark plug. Any suggestions would be helpful on these plans!!
Thanks again for the help

[skeeterBill200]

Well I got the gasket at a dealership this morning put the NTK 21006 O2 sensor on this morning and put it in the water the. Motor idles very good and WOT is 5950 rpms 72mph !! Thanks BuzzB8 for the directions this was pretty simple and cost $ 40.00 total with seafoam included!!

[BuzzB8]

[exttremeparadox]

I know i have been missing from this post for a while but i have been troubleshooting my issue as in depth as i can.

I ordered a used and calibrated complete set of injectors from BrucatoFIS.com. I installed per his guidance. I still have the same problem. I thought maybe i blew a hub on my prop but i marked it and it is good. I thought maybe the lower end has an issue so i changed the fluid and it look brand new. I replace ALL ignition coils and caps. Currently i'm going to run my boat at WOT with a fuel gauge attached and multi meter on the TPS. My guess after all this is the High Pressure Fuel Pump but i don't want to just drop the money on that without proof. The latest time i took it out to fish, when i went WOT the boat pushes water and goes no where. I asked my buddy to stand on the bow and the boat went on plane slowly. I could not reach full speed of 70mph but only 52mph before the motor started bogging down. When i got home, i ordered all new fuel filters and VST filter. I will take it out again and report back with fuel pressure, voltage and how she runs. Thanks to everyone.

[exttremeparadox]

Forgot to mention that i changed the Oxygen Sensor as Pro201 suggested.

[201pro]

What is the fuel pressure when you key on?

[exttremeparadox]

I will check it out but my memory says 35/36 psi

[exttremeparadox]

Forgot to mention that i took some advice and disconnected the switch by the shift linkage that drops two cylinders and checked and cleaned the fuel feed assembly just forward of the filter. I will run the boat on a separate tank of premixed gas and report back

[Thamelau]

I am assuming your motor has the same funcitonality as my '05 HPDI. If you disconnect the shift switch your motor will put itself into limp mode. It basically says "I started, but that switch says I'm not in neutral, something is wrong" and puts itself into limp mode. You need that switch operational.

[exttremeparadox]

Well this will probably be my final post on this motor. I have completed the following with no fix in sight:
- New Caps and Plugs; all coils check good
- New Low Pressure fuel pumps
- New fuel lines
- Cleaned VST and installed new filter
- New thermostats and poppet
- Throttle Position Sensor checked and within limits (.52)
- Fuel Pressure within limits (35psi)
- Used external tank to bypass boat tank in case of contamination
- Bought and used blink light harness to troubleshoot, light blinks with no indication of trouble
- Checked all oil lines for clogging
- Check props to make sure they didn't have a spun hub, no spun hub
- Checked Chris Carson Reed valves, all are seated and look great
- Reconnected Shift Switch
- Cleaned and inspected fuel pressure assy, check good
- Check and adjusted Throttle valves


Final run today on the lake was horrible. Engine idle was fast then slow and then died every time i tried to let it idle. Boat did get up on plane right away but now the idle is erratic and dies after idling for maybe a minute. I have invested so much time in this motor....is this how Yamaha is???? I'm so disappointed that I'm considering getting rid of it and purchasing a Mercury. I have been all over my area asking for a Yamaha mechanic to diagnose but no one wants to work on them....so as of right now the boat is dry docked and will remain until I can find a mechanic who will work on them or buy another motor. Thank you to all of you who helped me with this situation.

[wcs69rat]

Sorry to hear about your issues...I've been chasing similar problems with my 225 OX66. It appears that unplugging the rpm reduction switch on mine fixed my initial problem but the O2 sensor and plugs were then fouled from being soaked in oil due to misfiring and idling back to the ramp forever. Once I put in a new O2 sensor and plugs, it seemed to run fine. I've been chasing the issue of loss of power and WOT roll back for so long however that I don't want to get excited prematurely. Too bad I'm not somewhat close to you....I might be interested in purchasing the motor for parts if you got rid of it. Best of luck to you.