Could not find 50B - data below is for 50C...
Marathons in the list were... 60B, 70B, 80B, 100B, 40C, 50C, 60C, 70C, 80C, 100C, 120/150C
Manufacturer Potterton Myson Heating
Model Marathon 50c
Fuel Type Gas
Boiler Type Conventional
Method Non-Condensing
Flue Type Open
Fan No Fan
Output (kW) 14.7 - 14.7
Manufactured From/To Unknown - 1988
SAP seasonal efficiency 65%
Peccavi
May 2009