As far back as 1977, Bolens said the QT-16's were equipped as the following:
1973 # 1666-01 used Onan BF-MS/2425A
1974 # 1666-02 used Onan BF-MS/2425B & /2425C
1975 # 1666-03 Used Onan BF-MS/2938D
1976 # 1666-03 used Onan BF-MS/2938D & /2938E
1977 # 1666-03 used Onan BF-MS/3283F
Is your QT-16 a later model? ...Possibly this is where Garden Way got their info ?????
Mine has no serial number plate. The one on youtube is a 1973. The B43M-GA016 was 50cc bigger (still 16hp) and had an oil filter. I'm wondering if it might have been used in the first models-- or offered as a replacement engine?