  We investigate the viability of predictive schemes for quark-lepton Yukawa
ratios and nucleon decay in non-supersymmetric SU(5) Grand Unified Theories
(GUTs) where neutrino masses are generated by a type II seesaw mechanism. The
scalar sector of the considered scenario contains 5-, 24- and 45-dimensional
representations plus a 15-dimensional representation for realising the type II
seesaw. Predictions for the ratios of the quark and lepton Yukawa couplings
emerge when the relevant entries of the Yukawa matrices are generated from
single joint GUT operators (i.e. under the condition of "single operator
dominance"). Focusing on the 2nd and 3rd family and hierarchical Yukawa
matrices, we show that only two sets of predictions,
$\frac{y_\tau}{y_b}=\frac{3}{2}$, $\frac{y_\mu}{y_s}=\frac{9}{2}$ and
$\frac{y_\tau}{y_b}=2$, $\frac{y_\mu}{y_s}=6$ are viable. To further
investigate both options, we extend the minimal scenarios to two "toy models",
including the 1st family of charged fermions, and calculate the models'
predictions, e.g. for the nucleon decay rates and for the masses of the light
relics that are potentially within reach of colliders.
