T&T: Power Cord

[Ken Bloomfield]

Hi Steve,
I believe you will find that in practical terms there will be no difference. 
The boat, if wired for dual 30 amp, will almost surely have breakers that 
should open at safe levels, and the cables will therefor not be put to the 
test of trying to handle 50 amps.  Of course, someone will no doubt jump in 
and point out that the wires could short out boat-end prior to the breaker, 
thus drawing more than the rated 30 amps, but I believe that in that case 
the momentary current would be so high as to pop the 50 amp shoreside 
breaker long before the cable heated up.  Personally, I would not worry on 
that score.

Having said all of this, as I once before posted , I have seen more 30 amp 
cables have problems at the boat-end bulkhead than 50 amp ones.  I am not 
sure why this is the case, but it leads me to believe that one of two things 
is in play.  Either there is a tendency to run closer to the maximum rating 
with 30 amp services (was true in my case) thus proportionatly greater 
stressing the 30-amp connectors, or -- the 30 amp connectors are closer to 
the electrical "borderline" (i.e. less amperage headroom over their spec) 
than the 50-amp ones have.   I personally had 2 burn-outs with small (thank 
heavens) fires, and now have rewired my boat to full 50 amp service.  Prior 
to this while still in the dual-30 mode, I had solved the problem by 
replacing the boat-end bulkhead connector sockets from their original 30 amp 
genre to 50 amp capacity, and then replaced the boat-end connectors on my 30 
amp cables with mating 50 amp connectors.  Admittedly, that made the cables 
specific to my boat, but certainly reduced the fire hazard, and they could 
not be hooked up the wrong way either.  I must say that I am now much more 
happy with the single 50-amp cable, which offsets the fact that it is 
admittedly a bit heavier by not having to deal with the two-cable-tangle 
that about drove me crazy.

Just some added info for thought.

All the best with your next trawler.

Ken Bloomfield
Cell# 865-293-2174
MTOA# 2062
AGLCA# 3529
M/V Tellico Lady, 50' Marine Trader-Walkaround
Maryville, TN