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Author Topic:   Wiring High Current Loads To Engine Ignition Key Switch
just afloat posted 05-18-2008 09:36 PM ET (US)   Profile for just afloat   Send Email to just afloat  
Need advice as to the proper method of wiring a fused 1.5-amp circuit and a fused 20-amp circuit to be switched on and off with the key. The boat is a 2002 Boston Whaler Outrage with 175-HP OptiMax. Any advice where to find the switched color coded power would be greatly appreciated. Thanks
seabob4 posted 05-18-2008 09:46 PM ET (US)     Profile for seabob4  Send Email to seabob4     
Ignition Power (switched) is purple. There should be a pigtail coming off your engine harness by the backside of the keyswitch, also a black ground. That is your source for power. Wire those 2 to hot and ground buses, and all that you wire to them will shut off when you kill the motor.
jimh posted 05-19-2008 12:03 AM ET (US)     Profile for jimh  Send Email to jimh     
Adding a 1.5-ampere load to the ignition switch circuit is not a problem, but I advise caution in adding a 20-ampere load to that circuit. Check the engine service manual to see if the ignition switch circuit is capable of handling that much additional current. Usually the loads switched by the ignition key circuit are just a few instrument and engine-related accessories that do not draw much current.

The feed to the ignition switch is usually protected by a fuse. The rating of that fuse will give you an idea of what the circuit can handle, although you must allow for the current that is needed by the engine itself.

What device are you planning to install that will draw 20-amperes?

swist posted 05-19-2008 08:41 AM ET (US)     Profile for swist  Send Email to swist     
Just out of curiosity, how would you wire a higher current load through the ignition circuit than the switch is rated for?

Seems to me you would need to use the purple wire as the primary to a relay which would then switch a heavier duty circuit.

This situation must come up in certain boats, maybe just larger ones? It comes up all the time in automobiles, where the vast majority of electrical loads are ignition-switched.

seahorse posted 05-19-2008 08:48 AM ET (US)     Profile for seahorse  Send Email to seahorse     
20 amps through a key switch is probably too much.

Johnson and Evinrude specs are for a max of 5 amps coming off the accessory (violet or purple wire) side of the switch, not including gauges.

jimh posted 05-19-2008 09:10 AM ET (US)     Profile for jimh  Send Email to jimh     
A 20-ampere load deserves its own circuit breaker and should be wired with a minimum of 12-AWG conductor or larger if the voltage drop is important. The wiring in the engine harness that feeds the ignition switch is typically too small; I suspect it is probably 14-AWG or 16-AWG.

If the 20-ampere load must be operated by the ignition key switch, you should use a relay to control the current, and the ignition key switch will just operate the relay coil, which will draw much less current.

seabob4 posted 05-19-2008 07:47 PM ET (US)     Profile for seabob4  Send Email to seabob4     
Just what is that 20A circuit for? If it is for trim tab auto-retract, that circuit only draws a couple of amps. The tabs themselves draw about 15-17.
just afloat posted 05-19-2008 08:02 PM ET (US)     Profile for just afloat  Send Email to just afloat     

Thanks for the help, I tapped into the purple wire with only the EIC5000 (1.5 amps fused)and the trim tabs retracted upon turning off the key. The question and response from Bennett Marine below from the installation manual was the reason for my question. The Auto Tab Control power pigtail requires a 20 amp fuse. MJ Thomas from Bennett Marine responded to my question promptly. In his response he asked for feedback and would most assuredly appreciate the Input from this forum.
-----------------------------------------------------------To: Info
Subject: Step # 3 [Auto Tab Control] question

Step #3 Connecting the [Auto Tab Control] Power Pigtail
Does the orange wire have to be switched "on" with the ignition? Or can it be constant 12 volt powered by the Battery selector switch? Also installing the EIC5000 - Connecting the purple wire to the keyed switch - Is this connection independent of the [Auto Tab Control] pigtail to auto retract the tabs upon turning off the Key?

- - - - - - - - - - - - - - - - - - - - - - - - - - - -
Mr. Shattuck,

Thank you for contacting us with your questions.

You will need to connect both, the orange & purple wires, to a switched source, so they will not have power when you turn the ignition off. Please give this a try and get back to us with your findings.

We look forward to your reply.


MJ Thomas
Account Manager
Bennett Marine, Inc.
550 Jim Moran Blvd.
Deerfield Beach, FL 33442
Service hours: 8:00 am - 5:00 pm Monday - Friday (EST)
Phone: (954) 427-1400
Fax: (954) 480-2897

jimh posted 05-19-2008 09:02 PM ET (US)     Profile for jimh  Send Email to jimh     
Giving us the color of the wire associated with the loads does not identify the current draw anticipated on them. Could you redact your email so that it refers to the circuits by the current draw and not the wire color?
seabob4 posted 05-19-2008 10:16 PM ET (US)     Profile for seabob4  Send Email to seabob4     
On Bennett's website...both purple and orange wire are fused at 1.5 amps. The orange wire coming out of the auto-retract is simply to bring the tabs up, it is not to extend the rams or to be used underway, where you have hydrodynamic force against your tabs. The orange wire feeding your switch? Now that's another story. Wire both the "small diameter" orange wire and the purple to your ignition switch and enjoy. We use Lenco's, they have the same feature. In fact, all the engine manufacturers' today include a pigtail off of the engine harness to wire that feature into ignition.
jimh posted 05-19-2008 10:49 PM ET (US)     Profile for jimh  Send Email to jimh     
Bob--That sounds better. It didn't seem prudent that a manufacturer with as much experience as Bennett would be advising their customers to put a 20-ampere load on the key switch ignition circuit.
just afloat posted 05-20-2008 08:00 PM ET (US)     Profile for just afloat  Send Email to just afloat     
I certainly appreciate all the advice, I feel I should appoligize for my misinterpretation of the installation manual and low volt electrical. I must add that without your help, I'm not sure that I would be able to accomplish the install. After the comment about color wires and load requirements, I figured I'd better get back to Bennett Marine with just that question. If the orange wire in question was a small diameter wire, I probably would never have had a question. The [Auto Tab Control] pigtail orange is either 12 or 14 ga with an inline 20 amp fuse installed and shipped as a unit. The purple wire is 18-22 ga. shipped with a 1.5amp fuse installed. Instructions and advice from Bennett is to key switch both. Out of the water the trim tabs retract upon turning the key off with just the 1.5amp purple wire switched with the key and the orange 20 amp wired direct to battery power. I will remove the 20amp fuse and insert the 1.5 amp inline fuse, tie the two to the key purple and give it a try! thanks again

Mr Thomas,

I have had much discussion on line as to how to wire the 20 amp (not advisable) orange power [Auto Tab Control] connection to the Key switch. I'm questioning whether I'm supposed to insert the 1.5 amp fuse to the [Auto Tab Control] power pigtail along with the 1.5 purple power connection from the EIC5000 to the on - off key switch? Thanks again for your help.

Mr. Shattuck,

Yes and we would suggest connecting the both together, so you will only have to make one connection. Please give it a try and let us know your findings.


MJ Thomas
Account Manager
Bennett Marine, Inc

seabob4 posted 05-20-2008 08:32 PM ET (US)     Profile for seabob4  Send Email to seabob4     
Very interesting,
Just afloat and Jim, don't you find Bennett's answer a little puzzling? You have Bennett tabs, your wiring in a piece of their equipment, and the account manager doesn't refer you to the engineering department and then states, "Let us know how it goes.". THAT'S why we use Lenco's! Just afloat, I am going to email you the pdf from Bennett's site about wiring in the retractor. Then you can ask them about their technical advice. Let us know how it goes?
just afloat posted 05-20-2008 10:33 PM ET (US)     Profile for just afloat  Send Email to just afloat     
Thanks - The installation of the Bennett Auto Tab Control (ATC)in conjunction with the Electronic Indicator control (EIC5000) also requires reference to the Bennett Marine "Auto Tab Control Owners manual and installation instructions". The [Auto Tab Control] power pigtail @ the [Auto Tab Control] control unit is the Switched wire that was confusing to me. The [Auto Tab Control] manual instructions for the EIC5000 system instructs to follow steps 1,2, and the emailed question to Bennett step 3 in particular of the non hydraulic installation, therefore excluding step #4, which is the only reference for changing the fuse to the 1.5 amp. that I could find. I'm sure that installing both the [Auto Tab Control] and EIC 5000,and with both manuals to deal with, that I read into something more than I should have!
jimh posted 05-20-2008 10:49 PM ET (US)     Profile for jimh  Send Email to jimh     
When you used the acronym "ATC" in your narrative, I thought you were using ATC in reference to the fuses. The term ATC is a very common type of fuse used in many appliciations and particularly in 12-volt wiring and distribution. I had no idea you were using ATC as an acronym for "Auto Tab Control." I think this added to the confusion! I replaced "ATC" with "Auto Tab Control" where it was used above.

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