2002 Crownline 262 CR cabin cruiser shore power short

[dollar7499]

2002 Crownline 262 CR cabin cruiser with Mercruiser 350 B3 2 batteries, no galvanic isolator, do have Mermaid Air, hot water heater, stove, microwave, battery charger.

I noticed and posted a while back that my magneisum anodes were wearing fast on a 2 night stay in a salt marina, but I usually trailer to a freshwater lake, and use shore power very irregularly.

While I was rinsing bird poo off my boat in my driveway with the shore power adapter to an extension cord to my house, I noticed I was getting shocked while standing in a puddle and touching the swim platform handle. I turned off the battery charger switch on the panel and the shocking was still there, I turned off the 110v main switch and the shocking went away.
Those were the only two switches on. Note: I live in an old house that had two prong outlets and somewhere along the way someone installed three prong outlets but they don't have a wire to the ground plug. The whole house is two wire insulated wiring. That's what the boat was plugged in to.

What would be the correct method to tracing this down? I am a former (20 years ago) residential electrician and am an electronics technician, but have been unable to find Crownline AC schematics from pre Crownline bust in 2007.

Thanks!

 

[Scott Danforth]

trace the grounding and bonding on the boat

plenty of generic schematics if you google shore power isolation

 

[dollar7499]

OK I was able to find something by searching 'checking boat shore power grounding bonding with meter', anything with isolation in it gives 1000s of results about an isolator I don't have.
--One post says AC ground is only supposed to go back to the AC source, which my house doesn't have. Could this be the only issue?
--I bought this boat with no engine, and when I installed it, a ton of ground wires with ring terminals were right above the coupler housing (bell housing on a car) so I attached them to a stud on the block because they had that memory shape towards there... was that incorrect? no way they would reach the battery. (the battery ground wire is only 2 studs away)
--How do you read out the system to be sure?

 

[Silvertip]

Start at the house wiring and ensure that two wire system was installed correctly. So called "electricians" didn't always understand what could happen with reversed polarity hence one foot in the tub and touching the metal cabinet on a radio put you in a caskette. The newer three prong outlets have wide and narrow blades to prevent two prong accessory cords from being reversed. However, if the feed wiring is reversed you have a potential issue. If the house wiring is ok, THEN go the boat.

 

[dollar7499]

Silvertip YOU are the man! Plugged my outlet tester into the outdoor receptacle I always plug the boat into and it said 'HOT AND NEU REVERSED' so I switched the wires and it tests good now, I need to think of a better way to test the boat now than hosing down the ground and grabbing the rails. The outlet tester says the outlets in the boat are good, but are there any additional places I should ohm out to be sure?

 

[Silvertip]

If you have AC power into the boat, the very first outlet on a branch circuit circuit should have a GFI on it. Therefore, any grounding issues would trip the gfi. Each branch circuit could also be fitted with GFCI breakers. You can also do a voltage check between any metal object in/on the boat and ground. Any voltage at all would indicate a problem. But the problem here is the shore power has no ground so a it is likely a GFI or GFCI on the boat would not work.

 

[Silvertip]

I'll provide a bit of history regarding grounding of appliances. Back in the day of two wire AC wiring, the neutral (commonly but incorrectly called ground) side of the AC circuit was commonly connected directly to the metal chassis of appliances such as radios, electric fans, etc. The issue was that the folks doing the wiring in the day did not understand the problem with reversed polarity primarily because they were dealing with electric lights. When more modern appliances arrived, if the homes wiring was reversed, the appliance would still work but the chassis was now the hot side of the circuit. If you touched the chassis, a screw, a metal knob, etc., and then touched a metal water pipe you were greeted with a severe shock. If you happened to be standing in water and did the same thing you could end up pushing up daisies. So enter the three prong plug and the isolated ground in appliances as well as two wire appliances with polarized plugs. Theoretically that should have solved the problem but as you learned, improper wiring can still kill you. Amazing you can still buy replacement two prong plugs that are not polarized (both blades the same so they can be inserted either way). Electric companies in the early days should have recognized this danger and designed polarized two prong devices then. We would now have the need for 33% less wire). Instead we have this mish-mash of electrical stuff that the general public still screws up as do some so called "electricians".

 

[dollar7499]

I am going to run a dedicated new line with ground to a GFCI to replace this exterior receptacle on my house. Way cheaper than if this junk messes up my boat!

I will also check for voltage between ground and any metal in the 12v and 110v systems.