Gareth Jones chipped in with a half century, but it wasn’t enough to catch the away side.
The visitors set the standard by posting 204-1 from their 45 overs in this Lincolnshire County League Fourth Division fixture.
Mike Searle hit an unbeaten 102 while Dean Wright concluded the innings on 88 as Louth proved formidable with the bat.
Gareth Jones took the only scalp of the innings as he bowled opener Thomas Law for a duck.
In response, Horncastle lost openers Paul File and Jonathan Clark with neither scoring a run between them.
But number three Clayton steadied the ship, aided by Jones’ 64 runs.
However, with no other batsman reaching double figures, Horncastle fell short.
On Saturday the Firsts host East Halton in the Bob Welton Cup.
A day later, the Sunday Firsts host Owmby in the Lincoln and District League Division Two.