You can use a Grade 5 or Grade 8 bolt, but I’d stay away from stainless. Bolt size is 1/4-20 and 1-3/4″ length. That length may be hard to find at a hardware store but you can order online from Fastenal or McMaster Carr. A flat washer was used on the head bolts.
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
1982 Evinrude 25hp
“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
