yamaha ox66 225 issues

Oneshirthero · #1 08-09-2018, 09:06 PM

i have a 2001 yamaha 225 ox66 that has been giving me trouble for a while now. intermittent issues randomly idles high in neutral, at low rpms chugs likes is missing and randomly at cursing speed will drop 2 to 3 hundred rpms and pick back up. cannot idle through no wake zones when its happening just chugs like crazy.
i have replaced spark plugs, vst filter, fuel filter on side of engine, fuel water sep filter. low pressure pumps, o2 sensor and cleaned out sniffer tube. will run fine for a day no issues then all of a sudden it will act up. any help would be appreciated.

bradford · #2 08-10-2018, 04:54 PM

Bad coils or wires maybe? Sounds ignition related to me.

THEFERMANATOR · #3 08-11-2018, 11:29 AM

Have you put a fuel pressure guage on it and checked the high pressure pump output? Idling high in nuetral and chugging under load sounds like fuel starvation to me.

Oneshirthero · #4 09-15-2018, 03:33 PM

ok so new low fuel pressure pumps new o2 sensor and good fuel pressure throught rpm range
seems like is dropping cylinders when its not supposed to
while it was acting up i pulled wires on the plugs and the top left and bottom right were not firing

wellcraftv20step · #5 09-16-2018, 04:11 AM

I have been plagued with a very similar problem recently with my ox66. I was absolutely certain I found the problem by cleaning my injectors, but nope as of yesterday the problem is back, and that's why I'm up at 4am frankly.. it's got me losing sleep over it. !! I will now be putting a pressure gauge on it and see what that brings as Ferm suggests, but just because I decided to check my work and go over everything I've done already yesterday I pulled all 6 new spark plugs and found the bottom right ( not sure what number cylinder) plug to be spotless unlike the other 5, which makes me think it could be as Bradford mentions ,I'll let ya know.

SkunkBoat · #6 09-16-2018, 10:25 AM

Quote:

Originally Posted by Oneshirthero

ok so new low fuel pressure pumps new o2 sensor and good fuel pressure throught rpm range
seems like is dropping cylinders when its not supposed to
while it was acting up i pulled wires on the plugs and the top left and bottom right were not firing

I'm no expert but I do know that the OX66s don't idle in neutral on all cylinders. They purposely shut some down.

Oneshirthero · #7 09-17-2018, 11:50 AM

that ive seen but no body can come to a consensus on how it actually works.
changed the pllugs and ran great trolling and running for most of the day then started acting up again on the way home to the point of coming off plane.
at my limits with this motor not sure where to go from here.