The same risk of plugging is applicable to any marine engine, they all have to have a water intake to cool the motor, or they will seize up become useless.
Commonly used in these parts is a normal four stroke angine like a Briggs and Stratton with a long driveshaft inside of a tube with a small prop on the end- called a 'go-devil'....
They're called 'surface drive'....
These are currently being used in NO right now...
http://www.go-devil.com/GO-DEVIL_Engines.html
TS