Never been a fan of Johnson delt with a 40&4 two stroke but I bought a 15 to go on a zodiac 310 it was the commercial spec one we still have it at work not in use but I tell you what it made that 310 fly if you can get it at the right dosh get it simple engine no frills looked after should serve well
I had one, the GT which was sold as a 10hp with an easily removed baffle to put it back up to 15hp. It was a very sweet motor, and I’d say it was smoother than the Yamaha I also had at the time (ran them side by side on identical boats for a while).
It also had a front mounted gear change which was more convenient than the normal side mount.
Used 15 hp Johnson's exclusively in California in the 80's and 90's. Freshwater, saltwater, didn't matter, they were workhorses. I believe they were the same motor as Evinrude, just a different cowling.
Agree with above. They don't have the name or reputation of the Mercury, Mariner, Yamaha etc in the UK but are simple and usually robust motors. The advantage of their lower popularity should be a lower price than the most sought after makes.