Merc 115 thunderbolt

Itz gnome

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So I got this motor off a bass boat. Put it on my center counsel with a brand new control body. New ignition with push choke. The new throttle body has a pair of wires for the “neutral safety start switch”. What do these go to? Also do I need to connect the orange and brown wires if I don’t have a tach? I can get the motor to turn over but it will not fire. Ran before swap? Any help would be great!
 

Chris1956

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OK, I do not know what a control body is. Is it controls? If so, what kind of controls? Ign key in dashboard or on control?

What year and HP motor do you have?
 

Itz gnome

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It’s a new mercury control. Key on dash. Trim switch on throttle. It’s roughly 78’ 115hp . Mercury could not tell me the age of motor. Serial number to old
 

racerone

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So post your serial # or pictures of the decals.--------Some here can tell in seconds what the production year is.
 

Itz gnome

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[No message]
 

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Itz gnome

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Then it’s a 73 with a thunder bolt ignition. Put on Merc center counsel control.(purchased on amazon) with new cables. Wired everything up and now no spark. Motor fired and ran fine before swap.
 

Itz gnome

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Thank you for your feedback. I’m grateful for any help I can get. Carpenter by trade so if anyone in Green Bay wi area can assist I’d be more than willing to work trade for any help.
 

racerone

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----Thunderbolt was their name for electronic ignition.----Any pictures of the distributor / powerhead ?
 

Chris1956

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If that is a '73, you need power to the switchbox in order to have spark. Later models do not need power to produce spark, as the flywheel and stator produce it.

You also need to wire in the neutral switch.

The control should have the new wiring colors, and your motor the older wire colors, unless you have a new boat wiring harness.

How is the new harness connected to the motor?
 

Itz gnome

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I used the old wiring harness. Never took it off motor. I can get more pictures of motor this evening. How do I test switch box? I’m not great with electrical. My wiring harness has nothing that look like the (red/yellow) for neutral switch. I’ll get y’all pictures tonight. Thanks for the help
 

Chris1956

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OK, The S terminal on the ign key is for starter. That connects to one of the neutral safety switch wires. The other neutral safety switch wire connects to your yellow motor harness wire.

The I terminal on the ign key needs to attach to your white engine harness wire. This provides power to the Thunderbolt ignition system.

The C terminal on the ign key connects to the grey choke solenoid wire on the the engine harness.

The M terminal connects to ground. The other M terminal will connect to the orange wire, although your motor does not use it.

The B terminal connects to the red wire for +12VDC.

The brown wire in your engine harness is for the Tach signal. You may need to change the wire on the engine harness to use a modern tachometer.

That get it?
 

Itz gnome

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I’ll check into this tonight and send more pictures of the motor and key switch. At a quick glance I noticed I have different letters on my key back. The boat had a Force motor on it before. Do I need a different key assembly?
 

Chris1956

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OK, so new Mercury control, but old Force ignition keyswitch?

Usually ignition keys for outboards are pretty universal. Let me know what letters you do have on the ign key and maybe we can match 'em up.
 

Itz gnome

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Your the best! She fired right up! Thank you Chris1965
How do I tell if it needs a new impeller?

on a trim related note.
I have a blue and green for my trim. I wired both of them to what I’ll call a 5 prong relay. They were used in old motor. When I put them to my new control they both blew within minutes of operation. Is there a diagram that I can follow to wire these properly?
 

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Itz gnome

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This is the diagram I followed when installed. Grabbing new relays tomorrow to see if maybe they were just bad?
 

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Chris1956

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The original power trim motor on that outboard was a 3 wire motor. Blue, green and black. Black was ground, apply power to blue for UP and green for DOWN. Solenoids were used, versus relays.

The original power trim unit sat in the boat with 4 hydraulic lines running to the trim cylinders on the ourboard. The power trim motor/pump/reservoir used either one or two solenoids mounted on the unit itself. A simple switch was used for Up and for Down.

How about a picture of what you have?
 

Itz gnome

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I’ll be grabbing two new relays tonight. I believe I fried the old ones as I had power run to them from both the battery and switch. I can feel a click in the relays just no movement of trim. If I touch blue and green direct to battery I can make trim up and down.
 

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