Is there any way I can control which specific access point I connect (and stay connected) to from amongst a set of access points with the same SSID?

Question

I'm working from a boat in a harbor in which the ISP has deployed numerous access points around the periphery.  All the access points share the same SSID and each is configured to use either channel 1, 6 or 11.   From my location, there are over a dozen of these access points "visible" (based on the the output of WiFi Scanner) with a range of RSSI and S/N values that vary over time.
The ISP has told me that the quality of my connection should be "perfectly fine" for any access point with an RSSI value better than -75, but I know from experience that my connection quality is miserable (i.e. < 50Kbps download) for almost all of these, including those with RSSI values better than -75.  There is at least one exception, however, which gives me on the order of 2Mbps download, which is "great" in this context.
I've tried using a more powerful USB antenna plugged into my MacBook Air (mid 2011), but as far as I can tell, it really doesn't make much difference.  Neither does my location within the boat.   The overriding factor seems to be which access point I happen to connect up to.
I should point out that the closest access points are about 75 yards away, with many of them being several hundred yards away or more.  I'm guessing that even though the signal strength of some of the distant access points is causing them to get "chosen" some times, the results are unacceptable due to the distance.
I'm hoping that I can determine, through experimentation, which access point(s) provide(s) acceptable performance and then configure my Mac to limit my connection to those points through whatever mechanism I need to use (e.g. channel, MAC id, etc.).

Answer 1

Establishing a wireless connection with a client computer is left to the access point for various reasons. One reason that your Mac may not connect to the strongest access point is that it may have reached a limit of the number of clients it can serve, leaving it unable to accept a connection with another. The limit may not be very large.
Suppose that happens, and your Mac establishes a connection with a more distant access point having a weaker signal. Then, suppose a client drops off the network. Doesn't this mean your Mac will switch to the stronger access point? Not necessarily. The throughput delivered to and from your Mac would have to drop below a threshold specified in the AP for it to drop the client, leaving your Mac free to connect with another one. The reason for this is to prevent rapid switching from one AP to another in an area in which two signals are of approximately equal quality. If that were to occur the frequent and repetitive handshaking between the two devices would slow throughput to zero.
In an environment in which several access points are broadcasting the same SSID, Apple provides no insight as to how it determines which access point to choose. This is the reason I suspect this "choice" is a function of the router, or access point. The connection originates with it, not the Mac.
Now, what would solve your dilemma would be to determine a way to control the access point with which your Mac connects, by specifying the access point's unique MAC address for example. In this happy circumstance, you could maintain an editable "whitelist" or "blacklist" of the harbor's access points and be able to choose which among them you prefer.
I do not believe OS X maintains such a record of MAC addresses though, only those of the routers it uses. If I am correct about that, such a solution is unlikely to exist. Don't let that discourage you from searching for one though... I would concentrate on something like "selecting access point by specific MAC address".
I did find this patent application though:
Roaming Network Stations Using A Mac Address Identifier To Select New Access Point
Perhaps it's a start