As the CDU also signalled support for the SPD candidate, Weyel was elected as the successor to Jockel Fuchs as Lord Mayor in 1986 with a broad majority in the city council.

Weyel's term in office was marked by the noticeable ebbing of Mainz's rapid boom of the 1960s and 1970s, which is associated with the names of his two popular predecessors Franz Stein and Jockel Fuchs.

After the withdrawal of the US NATO forces due to the end of the East-West Conflict, the former military settlement at Mainz-Finthen Airfield was therefore declared a district of Layenhof.

On the initiative of Weyel and the head of the building department, Heidel and Schüler, the area at the southern entrance to Mainz was redeveloped (Römerschiff-Museum, DB-Cargo-Zentrum, Hyatt Hotel, and the Fort Malakoff Park, an office and business centre built by the Siemens-Nixdorf corporation).

Always strongly oriented towards consensus between the two largest parties, Weyel advocated the political Mainz Model, a broad coalition between SPD, CDU and FDP.