We present a comprehensive study on superconducting properties of Re$_7$B$_3$ and Re$_3$B through specific heat, magnetic susceptibility, resistivity, and transverse and zero-field muon spin rotation/relaxation ($mu$SR) experiments on polycrystalline samples. Re$_7$B$_3$ (T$_C$ = 3.2~K) is a non-centrosymmetric type-II ($kappa$ $approx$ 9.27) superconductor in the weak coupling ($lambda_{e-ph}$ = 0.54) regime. On the other hand, Re$_3$B (T$_C$ = 5.19~K) is a centrosymmetric type-II ($kappa$ $approx$ 34.55) superconductor in the moderate coupling ($lambda_{e-ph}$ = 0.64) regime. Our transverse-field $mu$SR measurements show evidence for isotropically gapped BCS type superconductivity with normalized gap ($Delta_0/k_BT_C$) values of 1.69 (Re$_7$B$_3$) and 1.75 (Re$_3$B).
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