By comparing the open-water characteristics and cavitation characteristics between the contra-rotating propeller boss cap fins (CRPBCF) propeller and the benchmark propeller, this paper investigates the influence of CRPBCF on the hydrodynamic performance of propellers. The CRPBCF model was constructed through geometric transformation of VP1304 propeller blades. Numerical simulations were conducted using the overset grid technique and large eddy simulation (LES) in STAR-CCM+. The computational results were validated against experimental data, demonstrating good accuracy and reliability. The results demonstrate that the CRPBCF propeller exhibits superior hydrodynamic performance compared to the benchmark propeller. At an auxiliary propeller speed of na = 37.5 r/s, it achieves maximum efficiency gains of 4.18% and thrust improvements up to 7.28%. In terms of cavitation characteristics, a distinct vapor volume fraction isosurface of 20% is clearly observed in the wake flow of the benchmark propeller, whereas no such phenomenon was observed for the CRPBCF propeller. This demonstrates that CRPBCF can effectively suppress the generation of hub vortex cavitation (HVC). In summary, the results demonstrate that the CRPBCF propeller not only enhances propulsive efficiency but also delivers greater thrust under low advance coefficient conditions while effectively suppressing the occurrence of HVC.