The ’64 RD is just your basic manual start, manual shift 40hp motor. Nothing scary about it.

I’ve found the 1960s 40 HPs to be good motors. The exception was the first year – the 1960. When they were new out of the box, they were known for bolts vibrating loose on the electric start motor mount bracket and it’s counterpart on the other side of the engine, and then these cast aluminum brackets cracked. I saw this first hand on 3 new ones friends had on my lake. When Dad bought his 1960 new back then, the dealer replaced the star lock washers with split-ring lock washers on these brackets before they let it out the door and it was OK. The next year the problem appeared to have been fixed by the manufacturer (according to the same dealer). We ran over 200 gallons of gas each summer through that, mostly pulling skiers wide open, and it was running good when Dad traded it five years later for a bigger one. The 1964 you asked about was different in that it was 50 to 1 gas/oil and the 1960 was 25 to 1.
Dave