No. Even when breeding 2 merles together, you have a 25% chance of getting pups that are non merle .
25% chance of homozygous merle (2 merle genes)
50% chance heterozygous merle (1 merle gene)
25% non merle. (no merle genes)
The about is of course assuming that neither parent is homozygous merle. If one parent IS homozygous, then you have no chance of a non merle.