ABSTRACT We use new precision measurements of black hole (BH) masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive BH mass. The megamaser-derived BH masses span 106-108 M , while all the galaxy properties that we examine (including total stellar mass, central mass density, and central velocity dispersion) lie within a narrower range. Thus, no galaxy property correlates tightly with M BH in ∼L* spiral galaxies as traced by megamaser disks. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed * the mean megamaser M BH are offset by −0.6 0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not appear to show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to an inability to resolve their spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.