Re: what auxiliary size
I have a 5.5 horse kicker on a 16.5 foot boat. It manuevers fine in any wind and water conditions, but I use it for trolling. I am not concerned if it pushes the boat faster than 2-3 mph, but if I ever had to get home with it, I would be there for a long time. Like JB said, it depends on what you will use it for. I prefer a smaller kicker working higher in its rpm range for fishing (mine is running a bit over 1/2 throttle to give me 2 mph). If it is primarily for getting the boat home, go for as large a kicker as a mounting bracket will allow (most are limited to 100 lbs). Good luck....
<br /><br />What would you need the aux engine to do?<br /><br />In sheltered water, as a "get home" engine I think as little as 6-8HP would do fine.<br /><br />But if you would need to overcome strong currents or winds and maintain steerage in rough water 15HP would be a lot better.<br /><br />Good luck. 
