Wiring Color Codes for Mercury & Mariner Outboard Motors. . Here is a listing of common color codes for Mercury and Mariner (US-made) outboard motors. These codes apply to later-model motors (approximately early 80's to present) mercury 135 blackmax tach sig - forums.iboats.com . Re: mercury 135 blackmax tach sig Your best bet is to get the service manual with diagrams in it. It will have the control diagrams in it also. Put the whole shebang back to original and fun out without worries. It sounds like the wiring is a little flaky anyway. Maybe the connector itself is dirty or worn and needs the pins spread a bit.