According to another wikipedia article, they are producing around 200 engines per year:
By June 2015, SpaceX was producing Merlin engines at the rate of four Merlin 1D engines per week, with a total production capacity in the factory of a maximum of five per week.
9 launches gives 90 engines (9+1 per flight), if I am not mistaken. That leaves 110 unused. There are also 45 recovered engines. In principle, SpaceX has a stockpile of Merlin engines for at least 11 launches, so what are they doing with all these Merlins?