attack convoy question

[I'm goin' down]

Is there a fundamental strategy for attacking convoys? I am on Mission No. 8 in Careers in a GATO. My sonar station is disabled, and I use auto targeting. I locate ships from the map and with my hydrophones. But when I try to engage a convoy I am always spotted by destroyers who see my persiscope even at night in a rainstorm. I am supposed to use my stadimeter while submerged to wait for the convoy to get close, surface and shoot, and then run away.

The destroyers have my number and are KICKING my ass.

[To keep myself occupied between attacks I am watching the original Texas Chainsaw Massacre, a classic because you never see any violence, but you see bizarre characters, bodies hanging from meat hooks, body parts, etc., hear victims' screams when the chainsaw is fired up, and see the remains after they have they have been "butchered." But nowhere do you see the actual attack--you only imagine it! ]