That is the last year for the 9.5 in production. They started production in 1964. Pretty much everything is interchangable from 1964, except for the cowling. 1966, they went to the lower lever lock, like yours has, whereas the 64 and 65 have the locking latch in the hood. Great old motors, but what a pain to work on.
I have a 55 hp seahorse that wont idle or rn under load unless it is half choked. If I cover the intake on the lower carb it makes no difference on how it runs but chokes it out on the upper one. Compression is fine on both cylinders as well as spark it acts like a vacumn leak but I cant find one. Any suggestions?
You need to start your own post so you woun't get lost.
If compression and spark are good, check the fuel delivery system, most likely will have to overhaul the carbs.