Problems with Smart Y Converter Box

It's been a very long time since I've used one, but I always had good luck with it. It will assure that your two 50-amp plugs are in-phase before combining them to your 100-amp cord. No (or very minimal) additional amperage draw.

These smart Y box work well. I ve used them many times and will deliver 100amps from twin 50s. As long as it clicks and the green light comes on it should be working

your problem is that you only have 208v at those outlets and the Charles can only do so much. At the same time while the voltage is boosted you are loosing amps.

What size boat, 95’? A single phase 100amp is not enough and you re going to have to reduce the loads. Shutdown one chiller and a water heater if you have two, etc. and possibly run a gen when cooking.

having spent 2 1/2 months juggling loads before i discovered I could just hook up to 480VAC, I feel your pain

There may be issues with the dock wiring. I've found that some marinas don't have 2 phase running down each side of a dock. In order to find two phases to get my smart-Y to work, I had to get the second connection from across the dock with a 15' shore cord.

The box will not connect unless you have two 50amp cords coming in and the phases are ok. When the breakers are turned on you will hear a click after a couple of seconds as the relays engage and the green light comes on. Indeed sometimes you have to find the right combo of outlet

I have always found that most marinas on the east coast are lagging behind in shore power. When I used to go up that way with a 70 footer I often couldn’t not find two 50amps

Yes, it was a known good "Y", so I checked the hots on the dock plugs and saw they were in phase. Fortunately, the maintenance man was there and told me about running the other phase on the other side of the dock. A jumper wire with my meter showed that 200+ volts was available. from both sides of the dock combined. This was with a 35A, 120V x 2-to-50A 240V Smart Y, but there could be similarities for 3-phase 100A.
After making up a short 35A shore cord for use under those circumstances, I was surprised how often I needed it. I ran that boat along both coasts of the U.S. and the Caribbean , so it came in handy.

Yes, same principle to power a single 50amp from a pair of 30amps (not 35 amps) than to power a single 100 amps form a pair of 59 amps

Both smart Y will only activate if both sources are connected and if the phases are ok

the only difference is that the 2/30 to 50 will only get you half the power (30amps) whereas the 2/50 to 100 will get you the full 100 amp. So, as long as voltage is good you will get the same amount of power.

Could be weak breakers on the shore pedestal.

If the iso transformer was working fine before what are the odds? Marina breakers are often overlooked by maintenance staff... at what amperage does it trip.

Is there really reason you want to stay in a marina with bad shore power? I know some places may be very nice and have great pluses but shorepower ai really critical.