Thank you for helping. See my responses below:
I don't think there is enough information to give you a guaranteed answer.
"I understand. I am new to boating
and this was my first post"
First, can you clarify what you mean when you say you tested the 50A connector and it is live. Do you mean the 50A socket on the dock or the 50A socket on your boat? If you mean the 50 A socket on your boat and you tested it and found it live (meaning you found 120V AC on the connectors inside the socket on your boat) while the 30A shore power cord is connected then you have a problem with your system and I would not connect another cord until you have it sorted out.
"One of the guys in the marina accidentilly touched the 50A pin and got shocked. So that is how I know it was live. I know - stupid move. The 30A side was plugged in already. I keep tripping either the shore breaker or breakers on the boat when I run a heater or two. So I wanted more power and bought the 50A cable. I just didn't know if I can plug both cables into the boat at the same time."
If you mean the 50A socket on the dock is live then you have one side of the connection OK.
"yes - 50A socket on dock is good"
Next question, there are two kinds of 50A connectors. The cord you bought is a 50A/125V but there is also a 50A/250V style that is slightly different. The edge of the blades in the plug bend inward on one and outward on the other. Does the plug on your power cord exactly
match the socket on the boat? Look carefully.
"I took a picture of the 50A connection and matched it up at West Marine"
To go to the next step you need to know how your boat is wired. You have to find out if the AC circuit breaker panel is wired to accept two different inputs at the same time or only one at a time. You could do this by checking with a meter or following the wires from the panel to the shore power plugs. If you don't know how to do this I highly recommend getting some expert advise before plugging stuff in.
"I have an electrical
diagram - but I am not an expert. So I will call an electrical guy to check things out."