1999 Yamaha 250 (OX66)
Per my previous thread at http://forums.iboats.com/showthread.php?t=450905, I replaced many of the fuel system components, but was still having issues with idle speed and WOT performance. Didn't have time to order/receive diagnostic equipment (out of stock/hard to find, etc), so I took it to my local marine mech who has all the test harnesses and Yamaha software (they used to be the local Yamaha dealer, but discontinued a couple of years ago).
They immediately found that the oil linkage rod has been incorrectly installed by the previous owner or mechanic, causing it to sit at the oiling position for 1/3 throttle at idle (that is the way he described it to me). Once that was done, they set the TPS voltage and also found that the throttle linkage had been manually adjusted way out of spec (probably to compensate for rough idle from over-oiling) The also put in a set of fresh plugs, recommending one heat range higher. Also ran a compression test and "checked the reed valves" and gave her a clean bill of health with the usual disclaimer about a sea trial before considering the problem(s) cured.
At sea, she purred at idle, shifted smoothly and seemed to smoke a lot less than before, however when trying to get up on plane she stumbled BADLY, sputtering and sounding starved for fuel until up to WOT. Then she leaped up on to plane and ran fine. I backed off the throttle and she again stumbled and sputtered badly. I had someone pump the fuel bulb while I was accelerating and this did not seem to make a difference. (All fuel filters are new)
On the water, I adjusted the TPS sensor clockwise and the mid-range performance improved noticeably with no harm to the WOT performance, but was still stumbling between 1500 and 2500. I went back, loosened the TPS again and rotated it ALL the way clockwise. Things improved more, but still running rough:
The O2 sensor was NOT checked by mechanic, I later learned. It is back in the shop today to run the factory test from the 2003 service bulletin (I printed off a copy and gave to mechanic)
Thanks in advance for your help or advice.
-Brent
Per my previous thread at http://forums.iboats.com/showthread.php?t=450905, I replaced many of the fuel system components, but was still having issues with idle speed and WOT performance. Didn't have time to order/receive diagnostic equipment (out of stock/hard to find, etc), so I took it to my local marine mech who has all the test harnesses and Yamaha software (they used to be the local Yamaha dealer, but discontinued a couple of years ago).
They immediately found that the oil linkage rod has been incorrectly installed by the previous owner or mechanic, causing it to sit at the oiling position for 1/3 throttle at idle (that is the way he described it to me). Once that was done, they set the TPS voltage and also found that the throttle linkage had been manually adjusted way out of spec (probably to compensate for rough idle from over-oiling) The also put in a set of fresh plugs, recommending one heat range higher. Also ran a compression test and "checked the reed valves" and gave her a clean bill of health with the usual disclaimer about a sea trial before considering the problem(s) cured.
At sea, she purred at idle, shifted smoothly and seemed to smoke a lot less than before, however when trying to get up on plane she stumbled BADLY, sputtering and sounding starved for fuel until up to WOT. Then she leaped up on to plane and ran fine. I backed off the throttle and she again stumbled and sputtered badly. I had someone pump the fuel bulb while I was accelerating and this did not seem to make a difference. (All fuel filters are new)
On the water, I adjusted the TPS sensor clockwise and the mid-range performance improved noticeably with no harm to the WOT performance, but was still stumbling between 1500 and 2500. I went back, loosened the TPS again and rotated it ALL the way clockwise. Things improved more, but still running rough:
- Idle: high 600's low 700's
- Started easily (first bump) while warm through probably 10 stop/start cycles.
- Acceleration feels very flat (lacking power) until hitting about 4000 rpms. Trouble getting up on plane unless WOT then backing off.
- Sputtering occurs right around 2000 rpms whether going up on the throttle or coming down.
- Fuel burn seemed higher than normal, but probably because so much time spent going to WOT and back
The O2 sensor was NOT checked by mechanic, I later learned. It is back in the shop today to run the factory test from the 2003 service bulletin (I printed off a copy and gave to mechanic)
Thanks in advance for your help or advice.
-Brent
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