getting a shock at gearshifter

[Rippin_54]

I have a 1968 650 merc, on a 15 foot aluminum starcraft. I recently have started getting a shock when i touch the gearshifter with one hand, and touch any bare aluminum with the other. Recently i have pulled off the distrubuter cap to clean it, and noticed where the screws hold the cap on was kinda cracked a bit, so i dabbed some silicon on it just to be safe. I have ran the engine in the dark to look for arking, and havent seen any. The engine runes great, but sometimes will short out and die due to this problem. it allmost feels like somehow the engine is sending spark thru the control cables, but i could be wrong.It sure feels like a spark shock I feel when touching it.
Any ideas on my problem would be greatly appriciated.

 

[Texasmark]

Re: getting a shock at gearshifter

Doubt that you are going to get a shock to your bare hands from 12v unless you are wet and really holding on tight to raw aluminum. I did see a guy standing in the water (saltwater) once trying to connect a battery in his boat. He connected the neg first (so the neg terminal was connected to the water he was standing in via the engine's lower unit which was submerged) and every time he grabbed the pos he got hit. I don't know how hard but he dropped the connector several times as soon as he touched the battery terminal.

Course had he reversed his connection sequence he would not have had a problem. He and the neg terminal would be at the same potential.
------------

That said, you must have some sort of ignition grounding out (the high voltage part) and it's doing it in such a way that you are experiencing what you are experiencing.

Possibilities are the cracked cover you spoke of; maybe more serious cracks. Other places could be where ignition wires are clamped to metal surfaces by metal clamps; even rubber insulated metal clamps.

Other than that, (don't know the '68 setup) you might have an ignition coil shorting out via the top insulators to 12v or gnd terminals, or internally.

Your night time test could catch some of the possibilities, but if you are shorting from a plug wire to a clamp internally, you probably couldn't see that.

Good Luck, best I can do.

Mark

 

[Rippin_54]

Re: getting a shock at gearshifter

thanx for the reply, yes i do agree, at first i thought it was a 12 volt problem, but then realized that the shock feeling i was getting was much stronger than 12 volts. I think this is going to be a tuff one to find. Do you have any suggestions (tricks) on how to find and pinpoint where spark could be jumping?, this is a real old motor, but still runs awesome!, and i really dont want to start guessing, and replacing parts that are still good. thanx again.

 

[Laddies]

Re: getting a shock at gearshifter

Your engine is a magneto powered and if the wire that come from the mag to grd the engine off is shorted or the ign switch is shorted and also the wire that grounds the box to the engine is broken. These are the most common places to cause the bos to give some one a shock. There is also a short ground wire from the mag or the block that can be broken.

 

[Rippin_54]

Re: getting a shock at gearshifter

one thing that i did do was, there are 2 wires that run to that tach in the gear shift control box that were badly corroded, and falling apart. So since i do not have a tach on the boat, i just cut them, and taped them up, just the 2 wires for the tach, there is 1 other wire in the box that looked like a ground that ran along with them, it was in better shape so i just cleaned it, and kept it connected. I dont think cutting the tack wires would cause the problem, but i have been proven wrong before.

 

[j_martin]

Re: getting a shock at gearshifter

Get a book and look up the wiring diagram for the control. You are missing a ground return to the engine, and the kill circuit is somehow shorted to the handle. Odds are when you repair the ground, the engine will be dead. Then you have to find the other bug.

Do it before you die, either electrocuted or run over by your own boat.

Hope it helps
John

 

[Rippin_54]

Re: getting a shock at gearshifter

so what you are saying is,, you think it is in the control box. I have been going over the engine, and cannot seem to see a ground problem, wiring is very old, and i have repaired some of it,, but i have also started the engine and pulled the big harness electrical connection from the side of the engine with it running. The engine still runs great, and i do not get a shock at the control box, but once i plug it back in i get the shock.
I have replaced the control box with a new one (used) was cheaper to get a used box, than order a new one, but still used the same ignition and choke, ect.

i am really stumped on this one. but would really like some advise on weather anyone thinks it is in the control box, or the engine, i am really thinking it is not a spark problem now.

 

[Rippin_54]

Re: getting a shock at gearshifter

i replaced the control box, not due to this problem, but because the big gears cracked and broke in the old one, but i have had this problem since i replaced it.

 

[ricksrster]

Re: getting a shock at gearshifter

First:
If your battery cables are part of the big plug on the side of your motor, DO NOT UNPLUG WHILE THE MOTOR IS RUNNING! It will ruin your rectifier.
Second:
Take apart the control. Look for bad wires, loose connections, etc. If you are not using that tach wire, you can disconnect it to see if that is the problem.

 

[Rippin_54]

Re: getting a shock at gearshifter

well been studying the wiring diagram, and noticed the diagram says on the coil, 2 wires , black& green, now on my coil i have a black and white. now i am guessing that the black should be ground and white hot. If i had these connected wrong, might be my problem, might try reversing these,, looks like i may have them backwards if the black is the ground.

Also i have no rectifier on this engine.

 

[Rippin_54]

Re: getting a shock at gearshifter

all right, i think i have narrowed it down to the merc switch (brown)wire being connected to the wrong spot on the switch box(was connected to the switch box ground which i moved to switch box blue), and the 2 wires for the coil.

This is my concern now, my wiring diagram says from the coil i should have a black and green wire , black getting grounded at botton of switch box, and green going to bottom terminal.

Now the coil i have which i think to be original but this is a 1968 and i am not the first owner has a Black and a White wire. The way i had it connected was black to the bottom switch box terminal and white to the ground, which i think might have been wrong, and might be causing the shock problem.

As of right now i have switched the wires, white to bottom terminal and black to switch box bottom ground, but i have now started to engine for fear of frying something.

As of right now i would greatly appriciate some advise on weather it is safe to try starting, if it will now do serious damage if i have the 2 wires connected wrong. I dont think it will, but have learned in the past, it is better to ask first. the serial number to the engine is 2353641

and i have figued it is a TYPE II ignition -- Thunderbolt distributer lightning energiser -- pointless (ignition driver)

and also just a question,,, what does that "mercury switch" do anyway?
i have scanned the wiring diagram, but cant figure out how to insert it into my post.

 

[Laddies]

Re: getting a shock at gearshifter

The black from the coil doesn't goto a terminal it goes to a scrw in the side of the box, heres a diagram

 

[Rippin_54]

Re: getting a shock at gearshifter

yes that is what i meant, at the bottom of the switch box, and it is a screw, i just wanted to make sure the black was ground, and not the white. The wiring diagram is a little different i have, type II, i believe you pic was type III , if i could just figure out how to attach it , i oculd show you

 

[Rippin_54]

Re: getting a shock at gearshifter

well fired it up, 60 degrees out right now, fired up at about 1 sec after hitting the key, no choke runs like a champ. Still shock at the control box. Maybe time to bring it in. Funny thing is runs the same with coil wire reversed

 

[ricksrster]

Re: getting a shock at gearshifter

The mercury switch kills your motor if you run over something and it tilts your motor up into the air out of the water. It helps to save the water pump from running dry.
Look at Laddies diagram and match your coil wiring to that.

 

[ricksrster]

Re: getting a shock at gearshifter

I think your short is in the control box.

 

[Laddies]

Re: getting a shock at gearshifter

The reason the engine fires up with the coil wires reversed, is on mercs CD ignition it's a AC system so technically they are transforers, not coils and AC current is not polarised.
If i were you I would start by removing the brown wire from the coil side of the switch box it serves no purpuse as it was the lead for the old style tach that is NLA. Also make sure the ground wires that bond the front cover where the switch is to grd.

 

[Rippin_54]

Re: getting a shock at gearshifter

i was wondering about the brown wire in the box, it is just screwed to a plastic plate, and i couldnt figure out its purpose.

I will remove it and see.

I was an apprentice on big trucks for a few years, and always considered myself pretty handy with wiring, bit this problem is really starting to make me angry.

Also could you explain what you mean by "Also make sure the ground wires that bond the front cover where the switch is to grd.", and does it do any harm with those coil wires being reversed?

 

[Rippin_54]

Re: getting a shock at gearshifter

LADDIES

you hit it, i removed the brown wire (from inside the shift box), and voila no more shock.

And it is definately the brown wire , cause if now since it is out, i grab the end of it, and then touch bare aluminum, and i get the shock i was describing.

now i wonder why power is feeding to this wire.

 

[Laddies]

Re: getting a shock at gearshifter

The early CD ign. the original tach had a high voltage adapter that changed the high voltage, about 90v AC to a pulse before it got to the tach. The problem was that if you got a short in that system it would kill the engine so merc started with a alt. driven tach so if it shorts out the alt. quits but you still can get to the beach. If possable to switch the coil wires I think I would-- Good Luck--Bob