Nearly ferromagnetic pseudobinary Lu(Co_Ga_x)_2 compounds have been investigated. The lattice constant increases with increasing Ga concentration, x, especially above x=0.09. High field magnetization and magnetoresistance of Lu(Co_Ga_x)_2 compounds have been measured in static and pulsed magnetic fields. No significant difference is obtained between the static and pulsed fields. A clear itinerant electron metamagnetic transition is observed and its critical field increases with increasing temperature for x=0.09. It is suggested from the discussion based on the Clausius-Clapeyron equation that the magnetic entropy of these compounds decreases above the critical field. This is consistent with the recent result of the electronic specific heat coefficient in the magnetic fields. The magnetoresistance of the ferromagnetic state after the transition is reduced about 30% compared with that of the paramagnetic state. This means that the metamagnetic transition results in a reduction of the spin fluctuation