I have a 250 salt water series that skips "stumbles" getting on a plane. It runs fine after it comes over the top. I have changed the fuel line, O2 sensor and now the stator. It has changed, but in a few times getting on a plane, comes back.
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1997 Yamaha 250
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seapro,
Seafoam is available at most major auto supply stores - I bought it locally here at Advance Auto.
It is a strong detergent, like Chevron Techron that Yamaha sells as "RingFree". It won't damage any of the components in your fuel system, including injectors. Just add it to your fuel tank at a ratio of 1 oz to 1 gallon.
Good luck,
Ken K
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Seapro25 -
My 1997 250 OX-66 was doing the same thing - I did the same things you have done - 02 sensor, plugs etc. It ended up being a stuck thermostat on the starbord side of the engine. If you are still running the original thermostats - take them out test them or just go ahead and replace them. It was causing 3 cyls to run super cool and causing the miss. It was also causing excessive carbon buildup on the plugs on that side of the engine and O2 sensor.
For about $40 you can order both t-stats and new gaskets. Easy to replace.
Might be worth a shot.. best of luck.
FWIW - I usually run ringfree in every tank.. Just tried the shock treat of SeaFoam (much cheaper than ringfree) and it seemed to work well.
Jack
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