  We study the experimental constraints on the Georgi-Machacek model from
direct searches for the new Higgs bosons and measurements of the properties of
the discovered 125 GeV Higgs boson. We apply these by interfacing the public
codes HiggsBounds 5.2.0 and HiggsSignals 2.2.1, which implement a large
collection of direct-search constraints on extra Higgs bosons and measurements
of the properties of the 125 GeV state to the model calculator GMCALC. We also
implement constraints involving searches for doubly-charged Higgs bosons and
Drell-Yan production of a neutral Higgs with decays to photon pairs directly
into GMCALC; these channels are not included in HiggsBounds but provide
important constraints on the model, especially at low mass. We identify new
constraints on the model from $H_3^0 \to Z h$ and $H \to hh$ and point out that
these channels remain promising. We also determine the allowed range of
couplings of the SM-like Higgs boson after all experimental constraints are
applied and show that the direct searches for additional Higgs bosons are
generally more constraining than the measurements of the 125 GeV Higgs boson
couplings. The updated GMCALC code will be released as version 1.5.0.
