Well BigMuz is taking some stick here for his large choice of aux, although he deserves some credit as you do see many large ribs with small aux's as an after thought, i.e 7.5m with a 3.3hp. Following on from Phil Davies's comment earlier today a 3.3hp will provide as much propulsion as a rampant rabbit
A 30HP Tohatsu 2 stoke is 51kgs and its 30HP 4 stroke counterpart is 69.5kg.
51KG is not a massive amount but they are awkward to carry and would be difficult to clamp on the transom in a rough sea. The ideal engine would probably be a 15HP or a 20HP, however, the Tohatsu 18HP is 41KG, for 10KG more you can get the 30HP with 50% more power.
Alex