I've just sold my 5.85m Inflatable which had a 50hp Yam hand stear. The fifty is quite a hand full to hand stear for any thing more than an hour at a time and thats on a big flubba.
We used to run 40hp hand stears on an 18ft flubba and that was okay, trialed a 40 hp hand stear on a 4m searider and that was lethal
Thus on a 4m ish flubba with a 50 is going to be more interesting than strickly nessecary,
Is there enough bouyancy in the stern of the boat to float such a lump?