Losing Speed before being able to snap and cutback

I'm currently having a problem with loss of speed after a bottom turn. I'm currently on an 6'4 NSP Fish (great slug of a thing) and I always get so close to being able to make a snap or cutback but end up wiping as I run out of speed. I think possible this may be to do with the type of board I have as it's very slow and heavy and so I have been looking at some other boards to help me get to the next level. I have so far tried a 6'0 Chilli STEPdown which I loved and I think that if the waves had have been bigger the day I hired it I would have been able to make the snap. I think I will definitely get a new board soon but I would like some advice on how to gain more speed or do better bottom turns to help me get back up the wave. Thanks 
