Actually, it doesn’t make a whale of a difference if it is a Sovereign or regular Buccaneer. Pretty much the same thing. But now that we are “discussing” it, how did you determine it is a 1959? 1958 Buccaneer 35 electric start was similar except for the Sovereign trim. Also, are you sure it is a 35hp? Again, 25hp and 35hp are similar in many ways. Does yours have compression relief valves in cylinder head (35hp)? A running change in 1959 (35D11 vs 35D12) was the tilt lock on the stern bracket. 35D12 series had the type shown in the inset. 35D11 had the separate knob.
