Re: need a can not find part for a mercury 150
this stabilizer/advance module served 2 functions, one was to alter the switchbox bias to advance timing if the RPM fell below about 600 RPM to stabilize the idle speed, the other was above about 5000 RPM it would add about 6* more ign timing, by altering the switchbox bias again, if all engine functions were perfect and the hull propped correctly and the correct octane fuel was used it worked very well.
it did not like 6 month old fuel, did not like a weakening fuel pump, any fuel restrictions, any varnish buildup in the main jet circuits or about anything else.
had they used a knock detect circuit like the EFI 200 it may have worked better.
but try to look up the bullitens on the spark advance or idle stabilizer module.
I normally dont reccomend trying to re-engineer products.
but do discuss this with your repair facility and do try to find the tech bullitens concerning the module.