Ox66 stalls under load at idle

[slcarley]

Spent a fair amount of time screwing around today - all cylinders have spark - event at idle - this is a 1997 ox66 EFI if that makes a difference (S/L 250TXRV).

I got it to stall a bunch and now I think I am hearing a sneeze!!! What the heck does that mean?

Plan to pull and change out the plugs tomorrow just because they look kind of "old". My charts call for NGK BR9HS-10. I presume that's the way to go.............

 

[seasick]

Spent a fair amount of time screwing around today - all cylinders have spark - event at idle - this is a 1997 ox66 EFI if that makes a difference (S/L 250TXRV).

I got it to stall a bunch and now I think I am hearing a sneeze!!! What the heck does that mean?

Plan to pull and change out the plugs tomorrow just because they look kind of "old". My charts call for NGK BR9HS-10. I presume that's the way to go.............

That motor will sneeze and often stall if the idle goes too low. Idle should be about 715 or so.

 

[seasick]

If it is idling too low, it could be as simple as an idle speed adjustment. It could be a throttle body valve syns issue or it could be more complex.
Use the shift override button while setting the throttle a bit higher. The stalling at low idel is more common when the motor is warm since when cold the ECU ups the idles speed

 

[lodgecreekgrady]

First thing you should do is run a compression test. Make sure you don't have low compression on one cylinder. To do this remove all spark plugs pull the lanyard (so no sparks), put the throttle lever in neutral mode and open it to full throttle for an accurate test. Compression should be around 120 but more important they should all be close to the same reading. Anything below 100 is a problem. If they are all good then check your o2 sensor. Remove the bracket from the side of the motor and there is an orifice tube that will carbon up, see if it is clear. You should be able to pull it right out. If it has carbon in it the clean it with a drill bit and some carb cleaner. Check the o2 sensor for carbon too. Clean it off if it does but do not use carb cleaner on the sensor as it may damage it. If all is good then you will need someone with a code reader to look at it.

 

[slcarley]

Been on a boatless vacation - continue to troubleshoot - changed the spark plugs - one of them was pretty well burnt. I'll start taking some of the other recommended steps this week. This is our second season with the boat - had the compression checked last year and all was good - this engine always stalled at low rpms under load (I'm particularly sensitive to it now because my slip is a little trickier to get into than last years).

I'll attack fuel delivery next starting with the lp pumps

 

[Toothpick 10]

Isn't it time just to pull the boat and bring it to a Yamaha mechanic? I think that you've been trying to solve this issue for about 3 weeks. I seem to read so many of these posts online with OX66s with folks spending all kinds of time and changing so many components and never finding the problem. What's an average shop rate, $100/hr? It probably takes a good and experienced tech about 2 hours to solve and fix the problem.

Remember, your time is worth something also. I not trying to be a jerk, but my feeling is if you can't solve the issue yourself within a day or two, you are at the point of diminishing returns.

 

[slcarley]

Toothpick 10,

I appreciate your input. I will eventually have my marina look at it if I can't solve it but in the meantime really don't mind puttering - just the opposite I enjoy it!!!

By boatless vacation I mean 300 miles away for the past couple of weeks.................