The Selway WEB site provides an excellent reference for many of their vessels, however you may need to be clearer in which individual hull you intend to choose, as the displacement varies with beam dimensions etc
The steam engine [installed] HP is listed for the majority of varients, and a few propeller sizes are listed [steam varients with oversquare diameter to pitch], however I would have thought most used
3 blade steam propellers over a
5 blade https://www.selway-fisher.com/Steam2030.htmThe
T12 or
T24 [12/24 volt motors from disabled scooter type things] are looking as possibilities, as would an automobile dash ventilation fan motor ....[similar to the T series] low speed, high torque, low current consumption ....OK with a 4" diameter propeller & suitable for R/C speed controllers...... so the motor canister diameter could be disguised in or as a ~~100 diameter horizontal steam boiler]
Derek