Headaches w/2000 250 OX66, Please Help!!!

[21Contender250]

I have a 2000 Yamaha 250 OX66 which has a rebuilt powerhead. The last few weeks I have been in the process of getting the motor rigged. Along the road, there have been a lot of bumps. Long story short, I had an oil pump problem which turned out to be a bad CDI Unit which has since been replaced. This past Saturday, dropped the boat in the water and it started right up. I noticed that it was running a bit rough, but, just figured it was from the double oil. Put the motor into gear and then I really could notice a problem. The motor is running as if it is in guardian mode and only hitting on 2 or 3 cylinders. I upped the RPM's a bit and the motor had nothing to give. It made the boat shake in the worse way possible. I immediately took the boat out of the water and back up to the garage. There were no alarms what so ever. My understanding is that the motor could be stuck in guardian mode. However, after I took the boat out of the water and went to run it on the hose, the motor only cranks over while not firing. I am at a loss for words right now. I became frustrated and called it quits at that point. Do you guys have any thoughts? Can't get the motor started to try and check sensors to see if that could be the problem. Please let me know what I need to check. Thanks in advance.

[boats.net]

Run ignition system test to find out why there is no fire, it could be anything like key switch, landyard switch, main wire harness, stator, pulsor coil, ECU, CPS and so on.

[tom976]

As for the spark, I would go with what was so far recommended such as switch, lanyard etc etc.

As for the rough running, that's more interesting....

Did you pull the plugs after the oil problem? (presume you were getting too much?)

After you get the motor running, the bottom two cylinders will deactivate when running below a certain rpm. You can check the 4 cylinders (top two on each side) for spark with a tester. Bottom cylinders can be tested only for a few moments on startup.

Did you have then block rebuilt recently or its just a motor that you got and was told that it was rebuilt? I ask this because sometimes things are replace and other can just be transferred over from the old motor. Things like the O2 sensor can also make the engine run like crap. If it was the original 02 sensor and its never been cleaned, oiling it too much isn't going to help it any.

[21Contender250]

The low pressure pumps are new. The VST tank has been serviced and the fuel pressure is holding steady at 36 lbs. or so. I will check out some more things tomorrow afternoon following work. As far as the kill switch goes, it has not been disengaged. Question, would changing out the CDI Units have any affect? Yes, motor has been rebuilt including new pistons, reeds, gaskets, seals, thermostats and waterpump. Thanks for the help so far!!!

[tom976]

You mentioned that the CDI was changed out.... Just out of curiousity, are you sure the plugs to the coil packs are in the right order?
I'd also check to make sure you are getting spark from the coils.

Have a pulled the plugs??? If they are wet I presume they are getting fuel so we can eliminate that out of the equation.

[Tucker]

Are you sure the oil problem has been fixed?? Since I got my OX66 I've read back through 100's of posts about OX66 engines and never read where a CDI caused any oil problems. I'd pull the plugs for a look.

[rwwillhunt]

Make sure your leads coming out of the CDI is going to the correct coils. I changed out a power head last year on my 1986 115 and had a similar problem. It would run but would not develop any power till I discovered this. Changed two wires and it runs like it should.

[21Contender250]

I first checked that the fuel pump was functioning when the ignition key turned on. Second, I checked each spark plug whiling finding 4 out of 6 plugs with very loose end caps. I went ahead and tightened down the four loose ends. Third, I turned over the motor and she fired right up. I then went out and dropped the boat in the water at the ramp as I could not find the muffs to fire her up again on the hose. So, I dropped the boat in the water while keeping her on the trailer and it would not fire. Turned it over and over, but, still no fire. Went ahead and took the cover off and confirmed again that the fuel pump was coming on when the ignition key was on. After a bunch of cranks, bang, she fired right up. It sounded rough again and about to stall so I adjusted the idle a bit higher. After it ran for a while at a higher idle and got warmed up, I put the cover back on. As soon as I put the cover on, she stalled. Took cover back off and she fired. Put cover back on while running and she stalled again. So, next time she was running with cover off, I fooled around with some wires. Here is where I found a 4 wire wiring harness at the top of CDI Unit and brown was only partially attached. Plugged back in and she was back to normal. Well, not normal, but, starting right up and running. Let her continue to run and then tried to rev it up there at the ramp. Still, not hitting on all cylinders. Tried putting it in gear and pushing the throttle forward and it had nothing to give and sounded like crap while producing the rough vibration throughout. As soon as you come off the throttle, the motor just about dies and sounds at its worse like it has a horrible virus. Anyway, the motor starts up as I have figured out the starting problem. But, we are back to the running very poorly and not hitting on all cylinders. Could it be the CDI Unit, bad motor wiring harness, etc.... I think we are close, but, still need some help. Thanks again.

[mitch]

have you looked at the oxy sensor


link thingy

http://www.boatsetup.com/O2sensor.pdf

[21Contender250]

I will be checking the O2 sensor tomorrow. As far as the CDI Unit goes, the oil pump in the remote oil tank was constantly running causing the onboard motor oil tank to overflow. At first, we thought it was the float, but, after replacing it and then testing both, we were forced to replace the CDI Unit and that was the fix. Thanks.

[tom976]

Ahh yes, those pesky loose plugs can do it to you....

I would still go over the correct order from the cdi -> coils. As I recall they just have a number on them. Put them out of order and it'll run like poop.

[21Contender250]

Fuel is new, fresh and stabilized in addition to the double oil. Original powerhead had an injector problem causing it to lean out. That has all been fixed including the main internal components replaced. I plan on checking the O2 sensor, changing out the plugs and checking the throttle position sensor. My understanding is that the throttle/gear position sensor could be bad while not allowing the final 2 cylinders to kick in.