BMC 1500 deisel Heat exchanger cooled engine with Thamesway marine reduction gearbox
Oil and water should be checked regularly. Antifreeze in coolant needed for winter.
Diesel fuel filter
Engine oil should be 10/40 mineral oil
Filter PMFL 31 https://www.oilfilter-crossreference.com/convert/POWERTRAIN/PMFL31
Here is a brand new similar engine..
Workshop manual
Gearbox Mk IV 2:1 reduction box
Gearbox oil (2 compartments) should be checked regularly
20/50 mineral gearbox oil
filter FRAM PH2869
https://www.oilfilter-crossreference.com/convert/Fram/PH2869