2004 OX66 225 will not get on plane or turn over 2000 RPM's and vibrates

[wcs69rat]

I have a 2004 225 OX66. When I took the boat out a couple of days ago, it idled fine through a very long no wake zone. Then it was very sluggish getting on plane and top speed was way down. Top end RPM was all over the place and would drop from mid 5000's to mid 4000's. When I got out of the throttle and tried to get back on plane, the engine vibrated and would not turn over 2000 RPM. I managed to limp back to the ramp at about 1000 RPM. I just installed a like new lower unit due to finding metal in my old one. The injectors were just cleaned and flowed. VST filter is clean. Low pressure pumps have been deleted and replaced with a Holley Red pump. O2 sensor has been modded to use the NGK O2 sensor and sensor probably only has 6 hours run time on it. O2 sensor dog bone cleaned approx. 6-8 operating hours ago. Pleated paper fuel filter was deleted when low pressure pumps were deleted. System has new RACOR 2 micron remote fuel filter installed with a 40 micron screen prior to the 2 micron filter. Compression is 105-110 psi on each cylinder. Plugs have approx. 6 -8 hours operating time on them. Engine seems to idle fine in neutral at approx 800 RPM although RPM does drop from approx. 600 RPM to 400 RPM in gear. Engine will rev and seems responsive if you give it gas in neutral. I have not had a chance to troubleshoot anything since getting back from the lake due to work.

If anyone has any ideas or has experienced this same issue, I would appreciate your input. Thanks in advance.

[RL552]

I have a 2001 225 ox66, with similar problem and have not been able to find the cause. If you figure it out let me know, if you would.

[yam911]

Any lights on the tachometer? Are they telling you anything?

[wcs69rat]

The only light I have on the tach that is flashing is the temp sensor indication that has flashed ever since I installed that digital tach a couple of years ago. It seems to be independent of the over temp warning, because the over temp warning does still function.

- Compression checks good
- Visible spark at all plugs
- All coil packs resistance check good
- Spark plug caps resistance check good
- New fuel line and filters (10 hrs ago)
- Injectors cleaned and flowed (10 hrs ago)
- Fuel pressure at 37 psi
- Stator coils resistance check good
- have NOT checked Lighting Coils yet: ordered a peak value adapter for my DVOM
- the two circuits of the pulsor coil seem to resistance check good. They are both within a few ohms of each other.

[wcs69rat]

RL552

Will do

[CJ1]

Disconnect the RPM reduction shift switch at the throttle linkage by the power head. CJ

[wcs69rat]

CJ1,

Will do. Thanks.

[wcs69rat]

RL552,

I haven't forgotten about updating you if I get my issue fixed. I disconnected the RPM reduction switch that CJ1 suggested and took it out to run it. It still would not get on plane and would not turn over 2700 rpm; however, it did not vibrate nearly as much as it did before and before, it would only turn 2000 rpm. When I got it home I pulled the O2 sensor and it appeared to be oil soaked. My thought / hope is that when I was limping it back to the dock for an hour prior to unplugging that switch that it loaded up with oil due to the mis-firing cylinders. I installed a new O2 sensor and plugs but have not had a chance to go run it again. I'll try to keep you posted.

[201pro]

I would try a new set of plugs. Where did you get the set that is in the motor now?
Lots of fake NGK plugs out there.

[wcs69rat]

Those plugs were fairly new and all had spark, however, I did install a brand new set the other day when I replaced the O2 sensor. I purchased the original set that had been in the motor for a couple of months from O'reilly Auto parts and the brand new set that I just installed from Auto Zone.

[CJ1]

replace the plugs and did you clean the draft tube for the 02 sensor when it was out? CJ

[wcs69rat]

CJ1,

Is the draft tube the same thing as the "dog bone" ? If so, it is clean and there is no build up at all on it.

[RL552]

RL552,

I haven't forgotten about updating you if I get my issue fixed. I disconnected the RPM reduction switch that CJ1 suggested and took it out to run it. It still would not get on plane and would not turn over 2700 rpm; however, it did not vibrate nearly as much as it did before and before, it would only turn 2000 rpm. When I got it home I pulled the O2 sensor and it appeared to be oil soaked. My thought / hope is that when I was limping it back to the dock for an hour prior to unplugging that switch that it loaded up with oil due to the mis-firing cylinders. I installed a new O2 sensor and plugs but have not had a chance to go run it again. I'll try to keep you posted.

Thanks wcs69rat

[Smallie_Hawgin]

Chipped, fatigued, and/or cracked reeds may cause some issues too. I ran into that with my 99 P200 TLRX (obviously not injected). In my case, I had corroded reed block and reeds that didn't seal all the time, surging RPM and not full RPM were my clues at the time. Easily checked on carbed models, not as easily checked on Injected models (that I am aware of). On carbed models you can remove the cover plate (silencer plate), place a cupped hand over the carb (in short bursts) and verify vacuum on two cylinders anyway. Replaced with Chris Carson Reeds and stuffer plates, problem solved. Full power, all RPM ranges, no surging, still some fouling, but that is inherent with carbed models running premix anyway... I am by no means a Yami expert, just passing along my experience. Best of luck with the diagnosis and fix man.

[bpicinc]

Chipped, fatigued, and/or cracked reeds may cause some issues too. I ran into that with my 99 P200 TLRX (obviously not injected). In my case, I had corroded reed block and reeds that didn't seal all the time, surging RPM and not full RPM were my clues at the time. Easily checked on carbed models, not as easily checked on Injected models (that I am aware of). On carbed models you can remove the cover plate (silencer plate), place a cupped hand over the carb (in short bursts) and verify vacuum on two cylinders anyway. Replaced with Chris Carson Reeds and stuffer plates, problem solved. Full power, all RPM ranges, no surging, still some fouling, but that is inherent with carbed models running premix anyway... I am by no means a Yami expert, just passing along my experience. Best of luck with the diagnosis and fix man.

Remove the reed plate assembly and pour some water in back side to check them. Mine were leaking, replaced them with the 2 stage Boysen Reeds.

[wcs69rat]

I had not read the last two comments regarding the reeds when I installed them but I just installed a set of Chris Carson reeds and stuffer kit. The stock stainless ones appeared to be fine but I figured it definitely wouldn't hurt anything.

[wcs69rat]

RL552,

As mentioned above, I unplugged the the RPM reduction switch that CJ1 suggested. The terrible vibration went away but it still had no power and would not get on plane. I found the O2 sensor soaked in oil, probably from the mis-firing and limping it back to the dock for an hour. I replaced the O2 sensor (I run the NTK 21006 so it was only about $30) and put a new set of plugs in. It seemed to run fine today. I guess I'll order a new switch and install it and see how it runs with the new switch connected.