The helicopter attacking Crockett's boat is an Aerospatiale SA342 Gazelle, but when it is shot down by the flare the burning and falling helicopter shown is Hughes OH-6 Cayuse.
The guy who shoots the witness after speaking with Crockett was unmistakably the same guy who backed up the shooter in the helicopter, yet Crockett didn't make the connection and had his back turned towards him when he shot the witness.
When Tubbs says the medivac is on the way, the shot is of the same old Bell 47G two-seater and not a medivac.
When Tubbs is searching for Crockett's boat, he is riding in a late fifties-era Bell 37G two-seater helicopter flying over a sea coast. The image cuts to the shadow of the helicopter but what is seen is stock footage of a sixties-era Bell UH-i helicopter flying over a forest.
Crockett shoots down a helicopter with a flare gun, but as it's falling, the rotor blades are already stationary.