Chrysler30fan first why do you want to change power head?
The 30Hp was produced first in 1973 with a new engine family 25 and 30Hp.
The 30Hp had a 1:2 (13:26) gearratio and a 10 3/8 dia prop. 25Hp had smaller drivshaft, 14:21 ratio and only 8 1/2 dia prop.
Then in 1976 there was a new 35Hp with in this family and the 30Hp dropped out.
30Hp had 468 cubic centimeter displacement and the 35Hp 559 cc
.
This 35Hp was produced then from 76 until 1981.
The 30Hp was back then in 1979 (as yours) and produced until 1982.
All these 30 and 35Hp from 1973 (not the 35Hp earlier then 1976) and up will fit your leg. Same bolt pattern and same drivshaft diameter.
The early 30 and 35Hp did not have CDI ignition, only magneto or battery ignition system.
Think the CDI was on from 1978 and up.
BTW Chrysler did not ever manufacture a 40Hp OB.
