I've now got all the club's results in a spreadsheet, so here's the list of 92 competitive fixtures where Boston United have conceded 6 or more goals!
Sat 16th Sep 1933 A M Barnsley Reserves 2000 L 2 9
Thu 21st Sep 1933 A C Scunthorpe and Lindsey United L 0 6
Sat 7th Oct 1933 A M Denaby United L 1 6
Sat 10th Mar 1934 A M Bradford Park Avenue Reserves L 0 12
Sat 31st Mar 1934 A C Gainsborough Trinity L 0 7
Mon 2nd Apr 1934 A M Grimsby Town Reserves L 1 6
Sat 28th Apr 1934 A M Hull City Reserves L 4 6
Thu 3rd May 1934 H H GRIMSBY TOWN RESERVES L 5 6
Sat 8th Sep 1934 A M Barnsley Reserves L 1 6
Sat 12th Jan 1935 A C Grimsby Town Reserves L 4 8
Sat 15th Feb 1936 A M Norwich City Reserves L 0 6
Wed 18th Mar 1936 A M Chesterfield Reserves 600 L 1 7
Wed 15th Apr 1936 A M Bradford Park Avenue Reserves L 2 6
Mon 19th Apr 1937 A M Gainsborough Trinity L 1 8
Wed 20th Oct 1937 A M Bradford Park Avenue Reserves L 1 6
Sat 7th May 1938 A M Bradford City Reserves L 0 7
Sat 31st Dec 1938 A M Peterborough United 2838 L 0 12
Thu 5th Jan 1939 H I CRYSTAL PALACE RESERVES L 1 6
Thu 25th Feb 1939 A C Gainsborough Trinity L 0 6
Thu 9th Mar 1939 A I Fulham Reserves L 2 10
Wed 19th Apr 1939 A I Crystal Palace Reserves L 0 8
Thu 4th May 1939 A I Brentford Reserves L 0 7
Sat 25th Nov 1939 A M Scunthorpe and Lindsey United L 0 7
Sat 6th Jan 1940 A M Frickley Colliery L 2 6
Sat 20th Jan 1940 A M Newark Town L 2 9
Sat 24th Feb 1940 A M Scunthorpe and Lindsey United L 2 8
Fri 22nd Mar 1940 A M Peterborough United L 0 6
Sat 27th Apr 1940 A M Newark Town L 0 6
Sat 2nd Feb 1946 A M Shrewsbury Town L 0 8
Sat 23rd Mar 1946 A M Barnsley Reserves 2000 L 2 7
Fri 19th Apr 1946 A M Grimsby Town Reserves L 1 6
Thu 12th Sep 1946 A M Grantham L 0 6
Sat 21st Sep 1946 A M Barnsley Reserves L 1 9
Sat 14th Dec 1946 A M Mansfield Town Reserves L 1 7
Sat 3rd May 1947 A M Scarborough L 0 6
Sat 31st May 1947 A M Denaby United L 1 8
Sat 29th Nov 1947 A M Frickley Colliery L 3 6
Sat 17th Jan 1948 A M Bradford Park Avenue Reserves L 0 7
Thu 7th Oct 1948 A M Goole Town L 0 6
Wed 23rd Feb 1949 A M Bradford Park Avenue Reserves L 2 8
Wed 6th Apr 1949 A M Bradford City Reserves L 0 9
Sat 10th Sep 1949 H M SCARBOROUGH 4183 L 3 7
Sat 21st Jan 1950 A M Denaby United L 0 6
Sat 21st Oct 1950 A M Mansfield Town Reserves L 0 7
Sat 17th Feb 1951 A M Nottingham Forest Reserves L 1 7
Sat 28th Apr 1951 A M York City Reserves L 0 6
Sat 16th Feb 1952 A M Bradford Park Avenue Reserves L 2 6
Sat 23rd Mar 1953 A M Mansfield Town Reserves L 3 8
Mon 6th Apr 1953 A M Lincoln City Reserves 6070 L 4 7
Sat 11th Apr 1953 H M ROTHERHAM UNITED RESERVES 3515 L 2 6
Sat 21st Nov 1953 A F Scunthorpe United 8894 L 0 9
Sat 28th Nov 1953 A M Grimsby Town Reserves 3024 L 1 7
Sat 27th Feb 1954 A M Mansfield Town Reserves L 3 6
Wed 25th Feb 1959 A I Wisbech Town L 1 7
Thu 9th Apr 1959 A S Gloucester City L 2 6
Wed 23rd Sep 1959 A S Chelmsford City L 1 6
Sat 3rd Oct 1959 A S King's Lynn 3742 L 1 6
Wed 21st Sep 1960 A S Folkestone Town 2464 L 1 6
Sat 8th Oct 1960 A S Yeovil Town 2208 L 1 8
Sat 19th Nov 1960 A S Cheltenham Town 1776 L 1 6
Sat 11th Mar 1961 H S CHELMSFORD CITY 1610 L 1 6
Fri 31st Mar 1961 A S Bedford Town L 3 6
Wed 12th Apr 1961 A S Oxford United 4647 L 2 7
Sat 15th Apr 1961 A S Tonbridge 1400 L 0 6
Mon 23rd Apr 1962 H P GRIMSBY TOWN RESERVES 1598 L 2 6
Sat 31st Aug 1963 H M GRANTHAM 1503 L 1 6
Tue 24th Sep 1963 A P Grimsby Town Reserves L 1 6
Thu 26th Dec 1963 A M Alfreton Town 795 L 0 6
Thu 16th Apr 1964 A M Goole Town L 0 7
Tue 21st Apr 1964 A M Lockheed-Leamington L 0 7
Sat 4th Sep 1964 H F SPALDING UNITED L 0 14
Sat 16th Jan 1965 H B SPILSBY L 3 10
Sat 20th Feb 1965 A B Spilsby L 0 7
Sat 20th Mar 1965 H B BRITISH RAILWAYS L 0 14
Sat 27th Mar 1965 A B Wrangle L 2 10
Sat 10th Apr 1965 A B Coningsby L 0 7
Wed 4th Dec 1968 A E Cambridge United L 1 7
Sat 21st Dec 1968 H N BANGOR CITY 2102 L 2 6
Wed 9th Jan 1974 H F DERBY COUNTY 11000 L 1 6
Mon 26th Apr 1976 A N Wigan Athletic L 0 6
Mon 26th Dec 1983 A A Frickley Athletic 482 L 1 7
Sat 4th May 1985 A G Altrincham 726 L 2 7
Tue 22nd Oct 1985 A G Wealdstone 628 L 2 7
Thu 5th May 1988 A C Northwich Victoria 399 L 0 6
Wed 28th Sep 1988 H C RUNCORN 2160 L 0 6
Wed 29th Nov 1989 A C Welling United 750 L 0 6
Tue 13th Feb 1990 A C Darlington 2940 L 1 6
Wed 27th Feb 1991 H C ALTRINCHAM 1201 L 2 6
Wed 16th Oct 1991 H L GRIMSBY TOWN 926 L 1 6
Tue 20th Apr 1999 A D Bath City 390 L 0 8
Sat 3rd Feb 2007 H 2 GRIMSBY TOWN 2915 L 0 6
Sat 8th Oct 2011 A N Altrincham 804 L 1 6