1983 Mercury Thunderbolt WHAT'S MISSING??

Bacon9209

Recruit
Joined
May 9, 2013
Messages
1
Okay, I have a 1983 Mercury 500 Thunderbolt that won't start. I had the carbs rebuilt last fall as they were shot. The motor starts when I touch the two screws on the side of the selenoid together with a screwdriver however I'd prefer not to start it that way and just use the key. When I turn the key 1/4 turn it turns the electricity on and the choke functions perfectly, but when I turn it fully over nothing happens. No click, nothing...

I was told it's either a selenoid problem or as you can see in this photo under the carb there is a small loop that appears it is there to connect to something however nothing is there. The other end connects to the shifter. What is that for? What part is missing? Should I replace the selenoid first and see if it turns over?

I scoured the internet and can't find a schematic for this motor anywhere. I'd really appreciate if someone could tell me the part name of what is missing. If you need more photos I can post them just let me know. I'm dying to hit the water and sick of the problems I'm having with this motor. The carb rebuild cost me about $200 and there is another problem. Just want to get it fixed and get fishing!
 

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Texasmark

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Joined
Dec 20, 2005
Messages
14,544
Re: 1983 Mercury Thunderbolt WHAT'S MISSING??

The ignition switch has an ON position which powers everything that needs switched voltage (as compared to hard wired to the battery), and a spring loaded second position (START) that sends 12v from that ign switch to the hot lead of the starting solenoid coil (the small 2 wires on the solenoid). The other small terminal is wired to ground (engine block or wherever the battery - cable connects).

Putting 12v on this coil hot terminal energizes a magnet in the solenoid and it sucks a copper disc down to contact the big input and output terminals on the solenoid. This powers the starter and when up and running releasing the ign sw takes power off the coil and the solenoid opens and the starter motor stops.

You can use a light if you don't have a meter, but I just gave you your wiring diagram. Putting the light bulb between the hot coil wire of the solenoid and ground and moving the switch to START should light the light....If not, switch in the control is bad or wire between two is broken.

If the light lights, listen to see if the solenoid clicks when it does. If so, that means that the magnet inside is energized and your control circuits for starting are ok.

Assuming an ok above, then the problem is internal to the solenoid high current contacts and get another....the contacts are pitted too much to carry adequate current to start your engine.

Simple as that.

Mark
 
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