5.0L TKS Component Identification

badrano

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In another effort to become familiar with my engine and how it's all wired together, I see a couple components that I can't find on any wiring diagram or I have questions about.

1. 15amp fuse on the aft engine harness. I see the 20amp fuse for the TKS module.
2. Relay off the harness behind the carb. Has Yel/Blk, Yel/Red, Blk, Red/Pur. I understand that that the Yel/Red is the starter line and it probably energizes the relay. This would seem to then power the Yel/Blk from the Red/Pur but I can't seem to find where the Yel/Blk wire goes.
3. Tan/Blu from a sensor on the aft part of the intake manifold. I'm thinking this is the overtemp alarm switch.
4. I see the oil press switch (Pur and Pur/Yel) for the TKS circuit and oil pressure sender (right side looking aft), but where is the oil press switch with the Tan/Blu wire for the low oil press alarm? Is there one? And also there is the Tan/Blu wire from the ICM.

Looking at the TKS wiring diagram, it would seem that if the TKS oil press switch opens, power to the fuel pump would be cut. These seems like an auto engine off if oil pressure is lost.
 

alldodge

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For V6 and V8 only

1. 15amp fuse on the aft engine harness.

What color are the wires?
If you have a Mercathode there would be a 20 amp mini fuse
Probably the fuel pump and oil switch

2. Relay off the harness behind the carb. Has Yel/Blk, Yel/Red, Blk, Red/Pur. I understand that that the Yel/Red is the starter line and it probably energizes the relay. This would seem to then power the Yel/Blk from the Red/Pur but I can't seem to find where the Yel/Blk wire goes.

Yel/Red - to starter solenoid (should be 10 ga wire to solenoid)
Yel/Blk - to neutral safety switch to ground
Blk - Ground
Red/Pur - From 50 amp breaker (from battery)
Should be a small Yel/Red to energize relay

Are you sure you didn't miss a wire?
Is this the standard slave relay or the square one?

3. Tan/Blu from a sensor on the aft part of the intake manifold. I'm thinking this is the overtemp alarm switch.

Correct

4. I see the oil press switch (Pur and Pur/Yel) for the TKS circuit and oil pressure sender (right side looking aft), but where is the oil press switch with the Tan/Blu wire for the low oil press alarm? Is there one? And also there is the Tan/Blu wire from the ICM.

The TKS oil pressure switch provides power thru the diode to the TKS module when the motor is running. It does not go to the alarm.

There should be a oil pressure switch on the top rear of the block with a Tan/Blue wire which is for low oil pressure alarm

The temp alarm swicth is on the thermsoat housing also with a Tan/Blue wire

TKS V6 and V8 wiring.jpg
 

badrano

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There should be a oil pressure switch on the top rear of the block with a Tan/Blue wire which is for low oil pressure alarm

The temp alarm switch is on the thermostat housing also with a Tan/Blue wire

On my thermostat housing, all that is there is the Tan wire (temp sender), Yel & Blk (temp switch to ICM). Next to thermostat on the manifold is Wht & Pink/Wht (TKS temp switch - Merc manual says it should be Orange and Wht). The TKS 20 amp fuse has Red/Pur & Pink/Wht. This makes sense...they may have had a shortage of orange wire that day :)

I found the oil press switch...it's on the back of the block. I thought this might have been the temp switch. Since the Merc manual shows a temp switch (the Yel & Blk wires) to the ICM, my temp alarm may come from the ICM since it has the Tan/Blu wire coming out.

The 15 amp mini-fuse has Red/Pur and Pink/Pur. Both are small gauge wire ~16 maybe 14 tops.

The relay is a square relay with only those 4 wires.
 

alldodge

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My manual is older and appears wires don't match

Colors
Red is battery
Purple is ignition
Black is ground
Any wire with a purple stripe is used for ignition
Any wire with black stripe is used in grounding

Red/Purple is fused battery power

The relay will have 2 small and 2 larger wires. Using your colors I would say
Red/purple main power
Yel/Red power to starter solenoid (if wire is a heavier gauge)
Black ground
Yel/Blk from key to start
 

badrano

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The relay will have 2 small and 2 larger wires. Using your colors I would say
Red/purple main power
Yel/Red power to starter solenoid (if wire is a heavier gauge)
Black ground
Yel/Blk from key to start

Looking at the merc manual that shows the wiring for the starter, where would the slave solenoid typically be located? I don't think I've seen such a "relay". The square relay in my case...all 4 wires are the same gauge ~16. My ignition switch has the typical wires (Red/Pur, Pur, Yel/Red).

I guess I can just pull the relay and see if the engine turns over :) Maybe this relay powers the slave solenoid...that would be interesting....key to this relay to slave solenoid to starter solenoid.
 

badrano

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Finally dug in to the harness and determined what the 15amp fuse is. It feeds the ignition switch off the 50 amp breaker. At this point it looks like the 50 amp breaker feeds a 15 amp fuse to the ign switch and the 20 amp fuse to the TKS temp switch as well as the line to the alternator and starter.

The engine harness connector doesn't quite have the same wire color coding on both sides.

The Pink/Pur wire from the 15 amp goes into the connector and then on the other side it's Red/Pur to the ign switch.

The relay in question is the starter solenoid slave relay. Yel/Red from the ign switch changes to Yel/Blk at the harness connector and feeds the relay. Yel/Red off the relay goes to the starter.

My boat doesn't fully match the wiring diagram in the Merc TKS manual :faint2: So if I ever turn the key on and the gauges don't come to life, I need to check the 50 amp breaker and the 15 amp fuse.
 

alldodge

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The Pink/Pur wire from the 15 amp goes into the connector and then on the other side it's Red/Pur to the ign switch.

OK the 15 feeds the Pink/Pur from the 50 amp
Thanks

50 amp breaker feeds a 15 amp fuse to the ign switch and the 20 amp fuse to the TKS temp

This clarifies the rest

50 amp feeds leg to 15 for ignition (ign fuse is on the motor and not under the helm)
50 amp feeds another leg to 20 amp for TKS
 
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badrano

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This clarifies the rest

50 amp feeds leg to 15 for ignition (ign fuse is on the motor and not under the helm)
50 amp feeds another leg to 20 amp for TKS

Is it a typical setup to have the ign switch feed protected by a fuse other than the breaker? It's interesting that the Merc manuals I pulled from iBoats don't show it.
 

alldodge

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Agree, but the fuse has always been up at the helm for the ignition fuse, this just has it on the motor
 

badrano

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Agree, but the fuse has always been up at the helm for the ignition fuse, this just has it on the motor

Just remembered this to...There is a 15 amp IGN breaker at the helm to. This must be the most protected circuit on the boat. :D
Maybe Merc decided to do something different for the 2009 TKS engines.
 
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