1999 OX66 Digital Tach-Temp Indicator & Alarm

I was previously looking at the wrong connector. I am sorry,
From the ECU on the there is a 4pin connector with a yellow, a Yellow-red, Black -red, and Green-red. Connected to a 4 pin( i beleive this is an extension) that goes towards the tach, it is a blue-white, Green-red, white-red, green on the opposite end of this is anothe 4 pin connector, which connects to the tach, The Tach however only has 2 wires in that 4 pin connector a Green-red and green-white. The green- red is matched to the white-red, and the green-white is matched to the Green throught that same connector.
The problem is that there is no overheat indicator on the tach and no buzzer sounding when it does overheat, however the safe mode on the ECU kicks in and drops the rpms. I Have replaved the impeller and housing with a complete kit. Part of the impetter melted and so did the housing the melted plastic partially obstructed the water output on the housing.

WHat might make it easier for both of us;
What wires from the ECU/motor harness send the signal to the didital tach causing the LCD symbol to light or blink, and respectively what wires on the tach do they connect to? Please? And do you have Rigging Diagram for 1999 ox66, I do have one for 1996 but I think it may be different.


Please help

[boats.net]

The wire colors change at connectors and some componets use same color wire, the pink wire at temp sensor activates overheat alarm and the pink wire at tach is trim signal wire.
Disconnect pink and black wire at temp sensor on heads and touch them togather(harness side) with key on alarm should sound and temp light should come on in gauge.

Thank you.
I tried that and no alarm or indicator.
The Tach is not recieving the signal. I am trying to figure out which wires from the ECU connect to those two wires in that 4 pin connector a Green-red and green-white at the Tach.
There are 4 wires as stated above that connect to the extension that goes to the tach , but only 2 wires from the tach to that 4 pin connector.
Nothing appears spliced or changed from factory set up.
Which wires from the outboard computer CARRY the signal to the tach and which tach wires are they supposed to connect to?

[boats.net]

Have you tested buzzer? disconnect wires to buzzer and connect to 12 volts to see if sounds alarm.
When you turn key on do you see temp light in tach light up for a second and go off?

Thank you for the recommendations
I will check the buzzer, I do see an LCD bar appear for a second or two when the key is turned in the on position. However it does not stay solid even if i connect the pink & black that goes to the temp SWITCH.
Should I heat up the temp SENSOR, if so at what temp should it give me an indicator on the tach?
Also if the lcd bar comes on when the key is turned is that a system check and if i am seeing a bar appeear for a secong or two does that mean the overheat indicator is working?

Another thing- I replaced the impeller, and the starboard bank of heads(170-190) deg is running hotter than the port(130-145). The pee tell tale is not very strong. The pressure relief is installed correctly and seated, not stiking.
I have taken off the starboard head & cover, and center section, found nothing. I suspect a blockage, where should I look ?

The water tube from the impeller going up to the powerhead, does that water get split and routed to each of the heads or is it a loop system where the water is pumped thru the port head first and then to the starboard head?

[boats.net]

The three bars on bottom right of tach is oil level, the temp light will be on bottom left side of tach if your tach has temp light. The older tachs did not have temp light, it was in speedo.