Hello Doc, I wanted to verify a few of the comments I'm going to make and these aren't being made to be disparaging.
1st I'll address pointing the Dish, one needs to take into account magnetic declination, by definition there are two different numbers for starting to calibrate a compass for accuracy. They are called true North and Magnetic (offset) North. Depending on the method or tool you used it could have an offset of 10 to 15 degrees here in the Northeast US depending on location.
Here's a link about Magnetic Declination,
http://www.rei.com/learn/expert-advice/compass-declination.html
Let me address SWM, this is known as single wire multi-switch. In your original post you said the Sat. receiver was only used on DTV's 101 and you used on your now defunct KVH C-3. This through me off since I thought the receiver wouldn't use SWM or look for any other LNB pointed at another TV-SAT.
Here's a nice link about SWM for those who would like to learn more about it,
http://www.swm8.com/swm-faq.php. I believe at home you may have the SL3S (3LNB SWM) and at the boat an LNB that pre-dates SWM. Hence the need to retrain your receivers parameters when going back and forth between both locations.
Now about the SWM or depending on the type LNB, I'm still not clear which you have? There are two varieties of the LNB - the SL3S (3LNB SWM) and the SL5S (5LNB SWM). Both work with slim-line reflectors.
I assumed (this can be a big mistake) you would be using a DTV old style 18" 101 DTV LNB and your receiver was set up for DTV 101 only.
As far as the dish style and type the receiver could care less if you are using an 18" reflector or a 12' large TVRO dish. The pointing gets more difficult as the dish size increases but the receiver doesn't compensate by either adding gain (turning up sensitivity) or attenuation (reducing gain) based on the type or size of the dish. What is important is properly matching the LNB to the receiver type for the service you want to receive.
Now I'm excited this has worked out for you. My Wife and I always enjoyed our morning coffee on our boat while watching the latest NEWs from DTV.
I hope this helps and I'm usually around if you or anyone else have additional questions.