Electrical shock on throttle ??

[lisfisher]

I have a question regarding my 1995 Mercury 75hp /shifter { quicksilver }. When I was on the water yesterday , I touched the throttle handle { metal part } and recieved a mild shock. My hand was wet at the time. It did it continuously every time I touched it but only when the shifter was in nuetral position. When in forward I did not feel a shock. I'm guessing this would be a ground wire of some sort but not sure where? Also , if this helps , when I returned home and parked the boat in the driveway{ on the trailer }, I started it up with the attatchment to flush the salt water out. I had it in nuetral and did not recieve a shock this time. Just wondering if this could have something to do with the boat being in or out of the water.

 

[Texasmark]

Re: Electrical shock on throttle ??

This was posted before and Laddies answered it but the engine was an old 4 cyl with a magneto......had magneto wiring problems. You don't have a magneto on a '95.

Unless you really try hard, you can't feel 12v. High voltage is only in the area of the plugs and wires. Might look for damaged insulation on your plug wires and clean up the grounds on your ignition modules.

Go from there.

Mark

 

[lisfisher]

Re: Electrical shock on throttle ??

Could it be a wire in the throttle itself? The entire ignition system was just replaced last season. Plug wires are also new but I will check them. What else should I be looking for? Basically any bare wire? And why would it not shock me while running in the driveway?

 

[j_martin]

Re: Electrical shock on throttle ??

It could be the ground wire is open to the controls. The kill circuit is high voltage, and would tickle. It is grounded to stop the engine.

 

[lisfisher]

Re: Electrical shock on throttle ??

I'm beginning to think it is in either the throttle itself or it happens only when the boat is in the water. Started it up again last night in the driveway after dark , sprayed all wires and connections under the cowl with a mist of water , even sprayed the mess of wires under the console panel , there was no arcing to be found. I wet my hand and touched the throttle arm and did not recieve a shock. Will have to test again while on the water. Where do I find the ground wire to the throttle control and where do I start tracing it from?

 

[Texasmark]

Re: Electrical shock on throttle ??

To get shocked you need a source of energy and a completed circuit. An example is placing your fingers on 12v battery terminals. You have the source of energy and the completed circuit is from one hand thru your body to the other. On the battery, if you lick your fingers and squeeze real tight you might feel a tingle. When you say shock I don't know how much you are talking about.

Here's a case that may give you some ideas:

I saw a guy in salt water once who had a dead battery observed after launching. He went to his truck and got that battery. He put the battery in the boat while standing waist deep in the water. He hooked up the ground wire barehanded (-) and proceeded to connect the hot wire (+) whereupon you could see him jerking back because he was receiving a shock.......because the circuit was closed.......battery - term to engine, engine was in the water, he was in the water, his hand was on the + wire terminal and when he touched the battery he had the completed circuit with the battery voltage across his body (lower torso to hand).

Now, had he connected the + terminal before the - there would have been no shock as he and the terminal he was trying to connect were at the same potential hence ho energy available to shock him.
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So, with what I have told you, think about what is different about the battery connections, any other metallic connections including water as a conductor....especially salt, and where you hands are (both of them) and other exposed body parts are when you get shocked, while the boat is in the water, and don't get shocked, when it's on the trailer.

Possibly you are only getting 12V and it is from possibly an ungrounded control box or something like that.....but that is pretty far fetched because the engine has to be grounded to the battery - to start it and the control cables would provide a ground to the control if nothing else did.

Get more info and come back.

I like your idea of looking for sparking at night. That was the right idea.
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Note on safety. The heart defibrillates (stops beating) at around 200 ma and that is lethal, as are higher currents, which can just plain flat burn flesh. The human body, across your hands...hence thru your heart....varies depending upon how good the connections are and how much salty sweat is on your body....or anything else that could improve the interconnect between the source of the energy and your body path thru your heart.

100,000 ohms is a good starting point for body resistance. So for the shocking current from getting your hands across your battery, you take 12v divide by body resistance (100,000 ohms) and you get .00012 amperes (120 micro amperes). So if you are real sweaty with body salt sweat and get a really good squeeze on the terminals, you might be able to get your body resistance (at the battery terminals) down to 10,000 ohms. That would give you a 1.2 milliamp current and that would be just a tingle (detectable sensation)......long ways from the 200 ma that would hurt you.

The guy in the boat had really good connections (with half his body in salt water) so he may have been down to 1000 ohms and felt 12 ma which was enough to make him turn the cable loose......course it probably startled him as much as anything.
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Mark

 

[lisfisher]

Re: Electrical shock on throttle ??

I can say this : Every time I feel the electrical pulse on the shifter , I think I've been barefoot , standing in a typically wet area of the boat floor. The water from the livewell spills out , goes underneath the console and runs across the floor to my standing area. Not sure if that has anything to do with it but it's a thought. The two times I did not get jolted { in the driveway } , the floor was dry and I also had shoes on. It's not a bad shock at all . just a strong tingle. Stator , power pack , ignition , key switch , plug wires are all new. Another thought is the fact that my throttle handle has been loose. I tightened it up last night via the allen head screw on the backside of the base.

 

[j_martin]

Re: Electrical shock on throttle ??

I'm beginning to think it is in either the throttle itself or it happens only when the boat is in the water. Started it up again last night in the driveway after dark , sprayed all wires and connections under the cowl with a mist of water , even sprayed the mess of wires under the console panel , there was no arcing to be found. I wet my hand and touched the throttle arm and did not recieve a shock. Will have to test again while on the water. Where do I find the ground wire to the throttle control and where do I start tracing it from?

The black wire in the harness is the ground return. It appears to be grounded at the stator in the engine, and it goes to the back of the switch, and to instruments. I don't know if it is grounded to the case or not.

That said, something is leaking to the case, and passing enough current to be felt. I would disconnect the harness from the motor, and from that connector probe the trim switch, power, and kill circuit wires, checking for leakage to the case of the control set. Likely you have a pinched wire or corosion providing a path to the case, causing the discomfort.

Hope it helps.
John

 

[lisfisher]

Re: Electrical shock on throttle ??

Now you have me thinking - I did in fact take apart the trim switch in the shifter handle because the copper piece inside was not making contact and thus , not working the engine up and down. I cleaned the contact point and all has been working well but perhaps I pinched a wire while re-installing the switch.

 

[Texasmark]

Re: Electrical shock on throttle ??

Looks like it's just battery voltage and you are on the right track. If your investigation of the switch installation doesn't work, you can take an ohmmeter, on the lowest ohm scale, put one lead on the batt neg term and (with the help of a piece of wire to get more length), go around the boat and insure that all metallic objects are within 1 ohm of the neg batt term. If you have to, run a separate wire and insure all connections are clean, tight, and brite. Once corrected, this should put a stop to your problem.

On your switch, you may have a dual problem: pinched 12v wire to the switch and bad ground on the housing allowing the 12v to be available on the control which is whats shocking.

Mark

 

[lisfisher]

Re: Electrical shock on throttle ??

one thing I can't figure out is why it only does this in nuetral and never in forward or reverse?

 

[j_martin]

Re: Electrical shock on throttle ??

PINCHED WIRE, only in neutral, never in forward or reverse.