Narrative:

On taxi out; the copilot was doing his takeoff briefing. During the briefing he made a comment about the N1 setting being too low. After his briefing; I asked him to take out the paper work and verify all takeoff settings; which he did. My paper work showed a 26K max takeoff and the ACARS takeoff data showed 24K max. We were 2;000 pounds lighter and he stated that we can do a 24K max takeoff. The N1 in the FMC showed about 85% N1. He stated that everything was correct for that power setting. The taxi checklist was completed. On takeoff roll the power came up to 84.7 and I noticed that the aircraft was slow to accelerate. I pushed the power levers up to about 93% with a slow rotation. On climb out I selected mct (maximum continuous thrust) and climbed out normally.we are not sure how this occurred. The copilot told me that the aircraft was scheduled to go to the wrong destination and he had to reload the FMC with a lot of changes. Somehow; a lower outside temperature was put in the FMC. The copilot doesn't remember how or when the lower temperature was entered. We contacted dispatch en route to let them know we had a problem with the FMC. We gave them as much detail as we could to see if they could figure out what mistake we made or if there was a problem with the computers performance. On landing; we called operations and were told that we had placed the wrong temp in the FMC during preflight.during the flight we pulled out the performance book and started to figure out what would have caused the FMC to show a lower power setting then what the paperwork from the ACARS would show. We determined that a lower outside temperature would have reduced the setting by the N1 that we had. On the taxi out we verified the settings and when the copilot looked at the N1 setting he said he saw 85% not 95%. When I asked the copilot to verify the takeoff settings; I should have delayed the takeoff until I had a chance to verify the performance as well. I knew the N1 setting was low; but with the length of the runway I didn't consider this too low of a setting. I did tell the copilot in the future; when you preflight the airplane and there is data in the FMC from another flight; to mention this to the captain. By doing this; this might have caused me to take a better look at the N1 settings; knowing that a lot of changes were made to the FMC during the preflight.

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Original NASA ASRS Text

Title: B737 Captain reports taking off with a calculated power setting of 85% N1 when it should have been 95% N1. Power was added during the takeoff roll when below normal acceleration was recognized.

Narrative: On taxi out; the Copilot was doing his takeoff briefing. During the briefing he made a comment about the N1 setting being too low. After his briefing; I asked him to take out the paper work and verify all takeoff settings; which he did. My paper work showed a 26K max takeoff and the ACARS takeoff data showed 24K max. We were 2;000 LBS lighter and he stated that we can do a 24K max takeoff. The N1 in the FMC showed about 85% N1. He stated that everything was correct for that power setting. The Taxi checklist was completed. On takeoff roll the power came up to 84.7 and I noticed that the aircraft was slow to accelerate. I pushed the power levers up to about 93% with a slow rotation. On climb out I selected MCT (Maximum Continuous Thrust) and climbed out normally.We are not sure how this occurred. The Copilot told me that the aircraft was scheduled to go to the wrong destination and he had to reload the FMC with a lot of changes. Somehow; a lower outside temperature was put in the FMC. The copilot doesn't remember how or when the lower temperature was entered. We contacted Dispatch en route to let them know we had a problem with the FMC. We gave them as much detail as we could to see if they could figure out what mistake we made or if there was a problem with the computers performance. On landing; we called Operations and were told that we had placed the wrong temp in the FMC during preflight.During the flight we pulled out the performance book and started to figure out what would have caused the FMC to show a lower power setting then what the paperwork from the ACARS would show. We determined that a lower outside temperature would have reduced the setting by the N1 that we had. On the taxi out we verified the settings and when the Copilot looked at the N1 setting he said he saw 85% not 95%. When I asked the Copilot to verify the takeoff settings; I should have delayed the takeoff until I had a chance to verify the performance as well. I knew the N1 setting was low; but with the length of the runway I didn't consider this too low of a setting. I did tell the Copilot in the future; when you preflight the airplane and there is data in the FMC from another flight; to mention this to the Captain. By doing this; this might have caused me to take a better look at the N1 settings; knowing that a lot of changes were made to the FMC during the preflight.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.