Hi Callum, I too got an old inflatable this year (zodiac) and i purchased an old Mercury 7.5hp to go on it. I spent a bit of time making sure the boat was leak free and i replaced an old patch that wasn't done too well and i re fixed the transom back onto the tubes. I then turned my attention to the engine. I got the old mercury running nice then added a kill cord (a must have item in my opinion). So that was the outfit sorted out the next thing i did was buy three life jackets. I had never taken a boat to sea so i tried my luck on the river Trent just to get the feel of it. I bought the boat to go cove hopping in Cornwall as there are plenty of coves that can only be reached by sea thus giving you a private beach for the day. I launched from a small harbor and kept close to the coast and found a great little cove. The hard part that i found was getting ashore. It was a calm sunny day but even so the breakers were about 2ft tall and they kept smashing into the boat wetting the three of us.Everything in the boat got soaked inc the towels. This upset my wife for a short while but we lay all wet stuff out in the sun and it dried out in 1/2 hr. We went on to having a perfect day in a spectacular private cove making getting wet well worth it. We came across the same problem re launching from the beach (those breakers never stop). The next day i returned to said cove on my own, i wore better shoes put all my stuff into a waterproof bag and instead of using the motor to come ashore i used my oars instead. I got within 10 feet or so from where the breakers were and dropped my anchor.The sea was around three feet deep but the fact that i dropped anchor meant i didn`t have to worry about the boat getting away from me. I then pulled the boat ashore using the breakers to help. Relaunch was just the reverse. So in just one day I went from floundering around looking like a Pratt to looking like i was competent in what i was doing. I guess I had learnt from my mistakes (the best way I find).
You can just rock up to your local beach and put to sea but some local restrictions do apply ie they will post on a beach notice board if your not allowed to launch motor boats ( parents get a bit touchy about getting their children`s limbs cut off with propellers)
I guess all the members of this forum have gone through the above at beginning.
Have Fun mate.