Moe, the icing is normal in the heat mode. In your house the unit has a sensor that detects the ice and puts the heat pump into a reverse cycle, thereby melting the ice. The units on boats do not have an auto defrost mode for when they ice up. The only fix is to switch over to the cool mode and set it for about 60 degrees. It will take a few minutes but you'll be able to see the ice melt off the coils. Once it does go back to the heat mode and you'll be fine. Keep an eye on it periodically and do a defrost when the coils start to become blocked. One tell tale sign is the heat output will drop off.
PS we have our new 43 October Moon at Glenn's as well. We're over on the pump out dock on the Winter's side of things.