UPDATE 2-Greece's PPC profit surges; outlook weighs

* 9-mth net profit 643 mln euros, vs forecast 623 mln

* PPC's posts biggest record quarterly profit

* Investors cautious on low visibility

* Stock down 2.3 pct

(Adds analyst comment, details)

By Harry Papachristou

ATHENS, Nov 10 (Reuters) - Public Power Corp (PPC) (DEHr.AT), Greece's biggest electricity producer, beat nine-month earnings forecasts on a sharply lower fuel bill, although investor caution on the state-backed company's outlook sent its shares lower.

PPC said on Tuesday net profit swung to a profit of 643 million euros ($963.1 million) in the period on lower power generation costs, beating an average forecast for a 623 million euro profit in a Reuters poll.

The result was a sharp improvement on last year's nine-month loss of 245 million euros. Third-quarter net profit reached a record 230 million euros.