I have not operated the Mk6 but the info. sheet I have states the following:
. recommended power : 86 kW / 115 HP
. maximum power : 131 kW / 175 HP
. maximum power with 2 engines : 2 x 52 kW / 2 x70 HP
. maximum engine weight : 240 Kg / 529 lbs
The max no. of persons for the Mk6 is 20. Commercial regulations may restrict that, depending on the type of operation. With 14 passengers plus the coxswain, fuel, batteries, auxiliary etc I think you would want a bit more power given that the recommended power is 115hp.
Hopefully someone else will be able to give you some better advice based on real world experience with the Mk6.