The black wire, the green wire and the yellow wire will give you RPM information on the tachometer.
Other wires are used to for the oil status lights. I don't think that vintage tachometer has an over temperature light.
The tachometer and its lights are unrelated to the warning horn. That is, the horn will sound and the motor will go into RPM reduction mode even if there is no tachometer installed.
What type of Yamaha control box do you have?
That is the Mercury serial number. You can go to the Mercury Marine website and insert that number into a search box. It will take you to the parts catalog for the motor.
The ECU is monitoring engine temperature. If and when the motor gets too hot the ECU will sound the alarm and put the motor into RPM reduction mode. The Command Link gauge will indicate the problem.
Is it all that important that the NMEA 2000 display indicate some particular temperature value?
An F25TXRD model came with a -30 ECU and a -50 wire harness assembly.
The first F225 with full Command Link capability was an F225TXR model with a production date of April 2005. It used a -31 ECU and a -51 wire harness assembly.
The -30 ECU was replaced by the -31 which was replaced by the...
What is the engine ID of your dad's motor?
Along with the ECU changes there have been some wiring harness changes. Need to make sure that the wire harness on the motor is compatible with a later dash number ECU.
Command Link is Yamaha's terminology for NMEA 2000.
If temperature sensor data is being seen on a Yamaha Command Link gauge, and other engine information is being seen on the Command Link gauge and on an NMEA 2000 display, I am not understanding why that data is not being seen on the NMEA 2000...
I had given the guy a link to where he could buy his manual in an earlier thread. $15 bucks for a pdf viewable copy. In response to a request of his. I can only guess now that he wanted a free manual. Obviously he did not buy the manual and came back here for free information. I don't suffer...
