I have a 94? Yamaha 150 TXRT that is missing at high RPMs.
Some facts ?
?Had the boat & motor for ~9 years.
?Integrated fuel tank of ~80 gals.
?~300 Hrs on the motor.
?Was missing at idle and sneezing to the point it would shut off. I had the carbs cleaned in January and it helped but it came back with the same problem. I later found a cracked fuel line going from the filter to the bottom carbs and fixed it. Sneezing problem seems to be gone and the engine idles fine. Now it has this high RPM missing issue.
?Changed primer bulb.
?Changed fuel/water separator housing and filter with all new parts.
?Changed spark plugs. Gapped them @10mm as per OEM.
?Changed the fuel filter inside the engine cowling last year.
?Runs at 4200 RPM max, not reaching the max power it once had. At max power, it runs at 4200 and it jumps to 4300 as it tracks the instantaneous power surges but returns to the 4200 range missing/surging. In other words ? power surges at full throttle are very rapid. No surging/missing evident at idle.
To me it seems like the engine has a restriction in one of the main jets or a bad spark that causes a cylinder to drop out and back at a fast rate (at high RPMs). I believe that the route to take is to troubleshoot the electrical to make sure it is not spark/ignition related before attempting to clean and refurbish the three carb assemblies.
Recommendations are welcomed!
Best regards,
Anglerfan
Some facts ?
?Had the boat & motor for ~9 years.
?Integrated fuel tank of ~80 gals.
?~300 Hrs on the motor.
?Was missing at idle and sneezing to the point it would shut off. I had the carbs cleaned in January and it helped but it came back with the same problem. I later found a cracked fuel line going from the filter to the bottom carbs and fixed it. Sneezing problem seems to be gone and the engine idles fine. Now it has this high RPM missing issue.
?Changed primer bulb.
?Changed fuel/water separator housing and filter with all new parts.
?Changed spark plugs. Gapped them @10mm as per OEM.
?Changed the fuel filter inside the engine cowling last year.
?Runs at 4200 RPM max, not reaching the max power it once had. At max power, it runs at 4200 and it jumps to 4300 as it tracks the instantaneous power surges but returns to the 4200 range missing/surging. In other words ? power surges at full throttle are very rapid. No surging/missing evident at idle.
To me it seems like the engine has a restriction in one of the main jets or a bad spark that causes a cylinder to drop out and back at a fast rate (at high RPMs). I believe that the route to take is to troubleshoot the electrical to make sure it is not spark/ignition related before attempting to clean and refurbish the three carb assemblies.
Recommendations are welcomed!
Best regards,
Anglerfan
