whites surfmaster2 beach hunt machine

[scrounger d detector collector]

i bought a used white surfmaster 2 it has an ambhibian2 coil. only 2 knobs. sens and disc. seems to get only about 4 in depth or so. when in the config to hunt salt water. u have to turn the sens down quite a bit or u get chatter and falses. who can tell me about the capabilities of this machine and how best to set it. when looking for small gold maybe it might be best to use more disc in order to keep sens higher. or hunt all metal w sens pretty low ? WOW WHAT A BATTERY HOG. WANTS NEW COPPER TOPS
and wont work on nimh rechargaeables. what is the engineering on this that it says
battey no good after alkalines are only about half used up compared to other machines?