A dictionary of Proverbs (Oxford Paperback Reference)

Do not spoil the SHIP for a ha’porth of tar
Ship is a dialectal pronunciation of sheep, and the original literal sense of the proverb was ‘do not allow sheep to die for the lack of a trifling amount of tar’, tar being used to protect sores and wounds on sheep from flies. Hog (quots. 1623 and 1670) seems to have been understood by Ray (quot. 1670 note) as a swine, but it was also a widely used dialect term for a young sheep older than a lamb but before its first shearing. The current form of this proverb was standard by the mid nineteenth century. The metaphorical phrase to spoil the ship for a ha’porth of tar is also found.

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  1623 W. CAMDEN Remains concerning Britain (ed. 3) 265 A man will not lose a hog, for a halfeperth [halfpennyworth] of tarre. 1631 J. SMITH Advertisements for Planters XIII. 30 Rather.. lose ten sheepe, than be at the charge of halfe penny worth of Tarre. 1670 J. RAY English Proverbs 103 Ne’re lose a hog for a half-penny-worth of tarre [(ed. 2) 154 Some have it, lose not a sheep, &c. Indeed tarr is more used about sheep than swine]. 1861 C. READE Cloister & Hearth I. i. Never tyne [lose] the ship for want of a bit of tar. 1869 W. C. HAZLITT English Proverbs 432 To spoil the ship for a halfpennyworth of tar. In Cornwall, I heard a different version, which appeared to me to be more consistent with probability: ‘Don’t spoil the sheep for a ha’porth of tar.’ 1910 Spectator 19 Feb. 289 The ratepayers.. are accused of.. cheeseparing, of spoiling the ship for a ha’p’orth of tar. 1992 ‘C. AIRD’ ‘Man Who Rowed for Shore’ in Injury Time (1995) 22 As Millicent, his late wife, would have said, it was just like Norman to spoil the ship for a ha’p’orth of tar. ■ meanness
  

ship see also one HAND for yourself and one for the ship; LITTLE leaks sink the ship; a WOMAN and a ship ever want mending.