Issues are "mounting", visibility in daylight situations, etc.

How are you going to be using it, John? For example, if you use one to paint the waterline, you really need to make sure that the boat is really "level" with respect to "its lines". Sometimes that is not with the mast perfectly vertical. I'm not sure you'd really be best with a self leveling unit rather that none that is also adjustable.

There are also some less expensive units. (Check Amazon, Ebay, etc.)