I agree with Windsperation but will add a bit. I have a 5hp Honda, it weighs 60lbs and is an effort mounting and removing but I leave it on the dinghy during season and tow the dinghy/engine together so that I do not have to wrestle with it all the time. It is not to hard to mount at the dock or shallow water at ramp so it only gets mounted once a year and I tie it at my slip.
I use mine for more than just dinghy dock service and find that 5hp is not enough power, 6-8 or maybe 9.9 would be better, especially for two adults. We like to explore, especially me, we can cover quite some distances around the protected islands as long a the seas stay relatively calm. There are lots of sheltered bays & inlets to explore and having extra HP gives you further range, but if that does not interest you then stick with the egg beater. I slip in Point Roberts and on a calm day I can travel half way across the Georgia Strait in my dinghy if I feel brave. The extra HP makes it a nice extra toy.