We present a tunable high power ytterbium fiber laser system which is suitable for a variety of applications in nonlinear frequency conversion, spectroscopy or in medicine technique. The realized laser system consists of a master oscillator power amplifier arrangement with a fiber integrated pulse shaper. The continuous-wave core-pumped fiber oscillator with a grating in Littman configuration as tuning element defines the spectral properties of the system, like tuning range and spectral linewidth. A fiber integrated modulator is used for pulse generation and shaping. The losses due to this modulator are compensated in a core-pumped amplifier. The final amplifier stage applying a double clad fiber generates peak powers at a multi Watt level. At a repetition rate of 20 kHz and a pulse duration of 3 μs an average output power of 1.8 Watt has been achieved corresponding to a peak power of 88 W. The system is tunable from 1040 nm to 1070 nm with a linewidth of 10 MHz. Experimental results on tuning performance, pulse shaping and stability will be presented.