Warning buzzer

Hi All,I could use some help on this one.I`ve read a lot of the post on warning buzzers,but i`m still confused on this one.I did`nt find the bass and walleye article Rodbolt referred to.I have a twin Yamaha 130 2-strokes 1995.I have all three oil lights on flashing,along with buzzer and limp mode.All oil levels are normal,and oil transfers normal.I replaced a rusty buzzer with a cole-hersee universal.this is when I noticed when I turn key on port engine port guage comes on and starboard guage also comes on.I can unplug port buzzer and starboard guage goes off.So I replaced port buzzer and when both engines are running everything works normal.No buzzers or lights except the one good to go light.Now if I just crank starboard engine alone after it runs a few minutes I get the buzzers and lights again then crank other engine and alls well.If I loose port engine it`s going to be a long ride home at 2000 rpm`s.I still feel like this is a low voltage problem but i`ll have to do some more checking.I would greatly appreciate any advice or suggestions .Also what is the electronic box at the buzzers called and what role does it have?Thanks James