They have been around since the year dot. The weak link is the VRO system, if it fails the engine is starved of 2 stroke oil and goes bang. Some most folk seem to eventually remove the VRO and use premix. There were premix versions shipped new as well.
However, I think the Evinrude, the marine and the Yamaha 2 cylinder engines share a lot of similarities, indeed we had a Yam 55 with a Evinrude engine cover for a while.
These 2 cylinder engines were produced in 50, 55 and 60 hp versions at one time or another.
Would I buy one? yes if it ran well but bear in mind they only have 2 cylinders so won't run as smoothly as a car engine, the condition is good and the price is right. Worth taking a compression tester along to check that both cylinders are similar. We had a pull start version which was hard work, the electric start version would be a bonus.
It would be a good sized engine for a 4.5m rib. We had one on a Humber Alpha 5m with 4 divers and kit and it would plane.
Ribnet is best viewed on a computer of some sort