Re: 1978 65hp Chrysler outboard
HA or HB does not matter, everything are interchangable. This enginemodel was intruduced in 1974 as 60Hp with 2 cyl. twincarb and 818cc displacement.
In 1977 it was rated as 55Hp and in 1978 there were one 55Hp 818cc model and one 65Hp 818cc model. The 1978 65Hp had a one piece gearcase (lager then before) and the 55Hp had the older two piece case similare or same as 35-55Hp from 1966----.
The blocks are same from 1974.... for 55, 60 and 65Hp but the gearcase are different. 65Hp has the lager one piece case. The weak thing on these engines are the ign.system. Chrysler intruduced the MAGII ign.system on 60, 105 and 135Hp in 74 and this system was no good. Offen the CD module failed and in 1978 Chrysler during warrenty delivered a retrofit kit (Prestolite system similare to the Prestolite system who was fitted to the 3-4cyl. models).
The waterimpeller and house are the same as for the 3-4cyl. models, I THINK.
Looking for parts then talk to Franz at Franz Marine, he has everyting. He is not cheapest but you know you get the right parts for you engine.
BTW. I have one 1978 65Hp and one 1977 55Hp both with MAGII ign.system of my own. I collect all used parts for these engine especally ign.parts to keep these engines in running contitions.