Begin with the boat
Hull size, mounting position, typical wind, water conditions and motor features determine what category of motor is appropriate. Check actual manufacturer guidance for the intended application.
Add the electrical system
Battery chemistry, charging compatibility, cable runs, overcurrent protection, connectors and access for maintenance are separate purchasing decisions. Verify them against the owner manuals rather than guessing compatibility.
Consider installation and storage
A quick-release bracket, battery restraint, corrosion control and winter storage may matter as much as a headline feature. Check whether the mounting surface can support the chosen system.
Plan for service
Find out whether replacement propellers, shafts, remotes and service centers are available. Total cost includes keeping a system functional beyond the first season.