It appears to be a VERY old Raritan Compact
Out of production for at least 10 years, replaced by the Compact II. From the looks of it, I'd guess it's original to the boat. I agree with wiseguy...don't waste your money on rebuild kit for a toilet that old, 'cuz the pump has to be so worn that a rebuild kit isn't likely to do much for it. Replace it (and all the hoses too...by now they have to be stinking or dried out and brittle). The current Raritan Compact II will cost you a little more than the cheapest piece of junk, but will be close to a "plug and play" replacement and a LOT higher quality, more durable toilet. The bowl looks to be in decent shape (can't see the condition of the seat and lid. So you only replace the pump/base assembly and recycle the bowl. That'll cost quite a bit less than the complete toilet, and save a LOT in shipping charges to HI, 'cuz bowls are heavy. This retailer http://www.boatfix.com/bypartnofrogpp.asp?partno=CPIIPUMP has the pump assembly (can't tell if it includes the base too...call and ask 'em) for $118.