Identify these wires

[robinsbd]

Hello,

I am trying to identify what these wires are for and whether or not they should be connected somewhere. One is back by the distributor coming out of the wiring harness and has a ring connector. The other is by the thermostat housing and has a slip connector. Please look at the pics below. Thanks!

 

[achris]

The spare black wire is a ground, and I suggest to connect it to the distributor body...

The other end (next to the thermostat housing) is a bit confusing. That switch is the water temperature sender, and should have the tan wire connected to it, not the black. (is your temp gauge working?)

Chris....

 

[Fun Times]

The eye ring connector should of been used/connected if your engine/drive combo model came with a Mercathode corrosion protection system as that is typically the ground wire for it.

The male spade by the temp sensor should be for Mercruiser's other carburetor / design choke they had....One style carburetor / design choke uses a ring similar to the one you show by the distributor though it shouldn't reach the carb that I recall while other carburetor / design choke design uses the spade type...Mercuiser often supplied both design ground wire connectors and used the design that fit while the other was just left unconnected tied back out of the way.

Lets see your carburetor choke design and wiring too and a better photo of your temp sensor with the black wire and then the black pulled away if not connected.

As that photo sort of looks like the ground wire may be touching the temp sensor body, Sometimes in diagnosing temperature gauge problems it may be suggested to try applying an additional ground wire to the temp sensor body to see if adding a ground will help make the temperature gauge work normal again.

 

[robinsbd]

The black spade wire by the thermostat housing is not connected to anything (just a bad camera angle). The pic below is the only pic of my carburetor I could find quickly. Sorry it doesn’t show the choke very well. I have rebuilt the carb several times, so I know it definitely has the ground wire that attaches to the choke housing with a ring connector.

The main reason I’m inquiring about the wires is because I was troubleshooting the ignition system electrical. My volt gauge has always bounced around a lot between 12 and 14 volts while running (very disturbing). I had already replaced the alternator, but still had this crazy voltage fluctuation. I finally resolved this issue. I found that the 10A ignition fuse under the dash had corrosion on one of the connectors. I replaced the fuse and moved it and the wire to a clean unused fuse slot. The gauges now are getting clean power and the volt gauge is reading 14.4 most of the time. The other disturbing part of this is that the same 10A fuse is also responsible for supplying power to the ignition module, sensor, and coil. The engine currently is not running well, so I am going through the wiring looking for more possible issues. Right now, I’m thinking the carb is “gummed” up again and that’s the reason for the poor running especially idling. My 2 barrel carb seems to be extremely vulnerable to issues. I’ve rebuilt it in previous years. This almost needs to be an annual task. The idle is rough now. When I slowly push the throttle up, it hesitates and stumbles and sometimes backfire through carb. If I push throttle quick past the stumble range, it seems to accelerate ok. I’m thinking carb again, but I can’t get out of mind about the thunderbolt V ignition module and whether it’s behaving badly or flaky. What do you guys think?