Mercury V8 300

V8 DTS model shown, others similar
a - PCM connector A
b - Main power relay (MPR)
c - Hot stud (battery +)
d - Fuse block
Connector Pin Wire Color Function PCM
86
87
85
30
59637
30 Red 12 V battery power (+) –
85 Red 12 V battery power (+) –
86 Yellow/purple Main power relay (MPR) control signal AA2
87 Red/white Switched 12 V power (+) –
1
6
A
C
65699
A1 Red Not shown –
A2 Red/pink Not shown –
A3 Red/white Switched 12 V power (+) –
A4 Orange/white Fused (10 A) 12 V power (+) ‑ O2 sensor –
A5 Red/white Switched 12 V power (+) –
A6 Red/yellow Fused (20 A) 12 V power (+) ‑ ignition coils –
B1 Red/white Switched 12 V power (+) –
B2 Red/orange Fused (2 A) 12 V power (+) ‑ RS48 diagnostic –
B3 Red DTS only; not shown –
B4 Red/purple DTS only; not shown –
B5 N/A Not used –
B6 N/A Not used –
C1 Red/white Switched 12 V power (+) –
C2 Red/orange Fused (2 A) 12 V power (+) ‑ fuel injectors –
C3 Red/white V8 only; switched 12 V power (+) –
C4 Orange/gray V8 only; fused (5 A) 12 V power (+) ‑ advanced sound control –
C5 Red/white Switched 12 V power (+) –
C6 Red/blue Fused (20 A) 12 V power (+) ‑ driver power CG3, CG4
Start Relay
The start relay is controlled directly by the engine PCM. When the PCM receives a start request, it sends a ground to the start
relay. The relay closes and sends power to the starter solenoid to crank the engine. Once the PCM determines that the engine
has started, it removes the ground from the start relay and the starter motor stops cranking.
105C
105B
109B
105A
d
RED/WHT
RED
RED
RED
YEL/PPL
YEL/PPL
RED/WHT
RED/WHT
RED/WHT
RED/WHT
ORN/GRA
RED/WHT
RED/WHT
RED/ORN
RED/BLU
RED/ORN
RED/YEL
ORN/WHT
30
85
86
87
A2
A1
H4
10A 2A
20A 5A 20A
20A
A1
A2
A3
A4
A5
A6
B1
B2
B3
B4
B5
B6
C1
C2
C3
C4
C5
C6
87
30
8685
A
B
C
D
E
F
G
H
1
2
3
4
A
B
C
D
E
F
G
H
H
A
4
1
B6 B5
B4
B3
B2
B1
C6
C5 C4 C3 C2
A6 A5 A4 A3 A2 A1
C1
a
b
c
65946
Actuators and Relays
Page 5B-6 © 2018 Mercury Marine 90-8M0146617 eng JULY 2018