Jandy, I cannot leave this alone. The more I read, more the fog thickens.
Confessions first: I started, own and act as Chairman of an ISP delivering broadband via wireless, many years ago using 802/b, now WiMax, and we install home networks all over the place. I have put WiFi on my boat.
Your solution is way expensive and unnecessary. To establish WiFi onboard and receive/transmit, you need an AP (Access Point) or Bridge from almost any major manufacturer. Cost $100 or less. End of story, until you want stronger signals.
For stronger signals, buy a bigger, passive antenna and run coax to the AP. I went overboard and got a 21dB round beam, which should theoretically receive and transmit a couple of miles with the above AP. You can do with less.
The AP point already has (cabled) Ethernet out, so to hook up PCs and the like you really need no more. For pure luxury, I added an Airport Express to run an indoor wireless net, but on a small boat, is that needed?
Apart from the very large antennas, all this is standard home equipment, and inexpensive. To me, the attempt to sell "marine" systems is profiteering on some innocent sailor's belief that radio waves must be different at sea. Bunkum all the way. Some might say "what about voltages?" but most of us already have converter solutions, and in any case if you're smart, eliminate the AP's supplied external power supply and go directly from the batteries - just match the DC volts needed. Some might say "IPX standards? What about waterproofing?" and my answer is "Why? The box is so cheap I'd keep it till it dies rather than pay twice for waterproofing; your onboard PC is likely of the same IPX class, but do you worry?"
Smear jelly over the coax fittings, and the antenna is waterproof. If cabling indoors for Ethernet, use the black outdoors Cat6 cable.
I won't go into a number of factual errors, but quickly: the 802 "n" standard has been with us for a long time. It may lack final official "standard" status, but all vendors from Apple to Linksys, Zyxel and TrendNet have had it in their boxes for at least a year. As for max allowed strength of antennas, 30dB is not a global standard. In my country the limit is 21dB, in others it varies.
For those interested in futures, look out for LTE and WiMax. Apart from Tonga and such, these nets mostly emanating from mobile phone telcos will soon match and supercede WiFi for most of us.