No. (assuming you are talking about a chemistry sample boat in this context)
Density is the ratio of mass to volume. Changing the contents of a boat does not change the boat itself. It retains the same mass/volume ratio. Even as a system, the weighted density (mass/volume ratios will not change).
This is different from “buoyancy” (water boats instead of sample boats), where the “system” is the total mass of the ship and contents, and the volume is amount of water displaced by the total mass. In that case, for a given ship volume, adding additional mass will increase the overall density of the system, because the volume is not changing while the mass is increasing.