Poor Math Grades, Mechanical Engineering

I’ve had fairly mediocre math grades in high school so far:

Geometry: A/A
Algebra 2: B/B
Precalc: C/B
Currently taking Calc.

How much will my math grades hurt me if I’m applying for mechanical engineering?

I have a 800 math, 750 writing, 750 cr SAT and a 3.95 CSU gpa, and a MCA of ~ 4600.

I’m not as worried about your math grades as I am about the quality of your math foundation and your ability to succeed at the next level. Math is a huge part of engineering. How advanced you are and how well you grasp it are probably the two strongest indicators of future success in engineering.