All mouth and no trousers

can anyone tell me if this is correct?
all mouth and trousers

Yes, that phrase is in Eric Partridge's book Dictionary of Catch Phrases: American and British, from the Sixteenth Century to the Present Day and is defined as "noisy and worthless stuff," applied to "a loud-mouthed, blustering fellow."

It must be a British phrase. I haven't heard it here in the U.S.

ALL MOUTH AND TROUSERS - "adj. British. Blustering and boastful, showing off without having the qualities to justify it.There is a suggestion that this is a corruption of a more logical, but rarely heard expression, 'all mouth and no trousers'. meaning full of talk but deficient in the sexual area. A less racy version is 'all talk and no action'. ." From the "Dictionary of Contemporary Slang" by Tony Thorne (Pantheon Books, New York, 1990).

On White Oak Mountain in W.Va., we called a boastful person a "blow George." In Texas, it is "all hat and no cattle."

"All mouth and trousers" and "all mouth, no trousers" are both still used interchangeably in the UK today, both meaning as described by previous posters.

Very similar expressions would be "blowhard" (archaic), "all talk, no action" or "he talks the talk but don't (sic)/can't walk the walk", which we've inherited from the US.

Means the same as "talks a good game" - i.e. likes to give the impression, but can't perform. The "no trousers" version implies lack of trouser furniture - no contents to trousers and the "mouth and trousers" version simply suggests that the bulge is only material with no meaty substance.
Whichever version you use, the meaning is the same : empty boasting.

See: the meaning and origin of the phrase 'All mouth and no trousers'.