Agent J you're right in your assumption, but adding ballast is a last resort. See how much of the "stuff" you've got stowed in the bow or under (or in) the wheelhouse that you can move further aft (or maybe ashore). Try to keep your fuel tanks full. If your water tank is forward, try running with it only half full unless you think you NEED it full.
If all else fails I'd get a couple 30-gallon plastic drums from a used-drum place (they're cheap) and secure them in the engine room. Then put in just enough water to get the trim you like. If you get clean food-grade drums you can incorporate them into your water system. Bear in mind adding ANY weight slows you down and costs you fuel $$$$.
However the wandering seems to be common with single screw houseboats, even properly trimmed. Practice and experience seems to be the only solution. You probably bought it to USE... so use it, and the practice and experience will come.
Big, heavy, slow vessels are slow to respond, period. Most newbies get impatient and use too much rudder, then when the boat does respond it goes too far too fast and you need to apply rudder the other way to counter the swing. If you're not careful you're all over the place. Use as little rudder as possible, be patient and give the boat time to respond. As soon as it starts to swing take some or all of the rudder off and let momentum work for you instead of against you.
You have a relatively flat bottom and lot's of "sail" area, so a light puff that you wouldn't notice in a different boat can push you off course. This combined with the above can drive you nuts till you learn the touch. It's sort of like riding a bicycle; there's a trick to it that you have to learn, and the only way to learn is to take the boat out and use it.
She's a tired old barge but she's paid for! http://s71.photobucket.com/alb...p;current=ef324993.pbw
06:45:05 PM by