Her burial has Elizabeth SAYLE, 89, Ramsey, buried Maughold June 8 1829.
So b.c.1740 according to this.
As a Ramsey family her children's bapts would be in Ramsey, so you need to look at these in the MM or on LDS film no.0106741.

Her bapt probably Elizabeth daur of William Wattleworth & Margaret bapt Parish Church Maughold 1 Jun 1740.
Siblings were John bapt Parish Church 14 Mar 1741/42, and Catherine bapt Parish Church 11 Apr 1744.
Margt infant of Wm WATTLEWORTH buried Maughold Jan 26 1746.

I can't see a marriage between William Wattleworth & Margaret in Maughold, but this burial could give a clue:
Wm Son of Wm WATTLEWORTH & Margt CURLETT buried Maughold May 20 1753.
(See his baptism 1749 in Ramsey, and sister Margaret 1753, on the IGI under only their father's name.)

A Wm WATTLEWORTH was buried Jun 9 1795, in Maughold, and a Margt WATTLEWORTH was buried Apr 9 1803. Or they may be in Ramsey records, rather than Maughold.
Brian Lawson's wills index has one for WATTLEWORTH, William 1803 Maughold E 2 0106408 which would be well worth getting, because I didn't see another William W in Maughold records at that time. It may have gone to probate after Margaret's death. See at MM or on LDS film no.0106408.

There are several brief mentions of William Wattleworth in Constance Radcliffe's book about Ramsey 1600-1800.

I think he was probably the son of well-known "John Wattleworth senior late Captain of Ramsey". See John's will transcribed by Joyce Oates at: www.iomfhs.im/lawsons/LawsonBMD/twill/1741_019.html
You may be able to confirm this from William's will, and it would be helpful to send a transcript of this to add to the Wattleworth ones on the wills index.

Sue