Now that I've got your attention:

We just bought a 1978 Nautaline 43'. I'm trying to learn the "systems". It has a lectra-san. A 1.5" hose coming up from the floor is capped off- I'm assuming that is the hose to the holding tank. There is a "waste" port on the port side and the original paperwork mentions the boat is equiped with a holding tank.

Question: Is there access to the middle of the hull to inspect/replace the holding tank and freshwater tank? Maybe its been carpeted over.

1st of many questions....

Thanks in advance!

Have the guy that surveyed your boat go over it with you. He will be able to explain each system and how it works.

Thanks! I think I've gone about as far down that way as I can go, though. He just knows there's no access he can see to the tanks. Nautalines are pretty rare out here (Sacramento Delta) and I'd like to communicate with other owners on the peculiarities of this make.

But I will talk to him again about the generic stuff.

I've got a 74 model 43' and I can tell you how mine is, don't know if it will be the same thought.  My holding tank is located in the floor on the lower level.  When you step down the stairs to the lower level, I have to remove the steps, pull back the carpet and there is a piece of plywood that is able to be removed.  Underneath this lying in the hull is the holding tank.  To gain limited access to the hoses, etc I can remove the back paneling in the closet near the bathroom and this is where the line runs from the holding tank to the discharge port.  My boat when I bought it had what may have been an original holding tank, or at least an old one that was in the same spot, but was basically dry rotted and in pieces.  This boat had the purasan system, but since we moved to a no discharge lake, I replaced the tank.  I can't help you on the water tanks, I am assuming mine are or are supposed to be in the hull near the rear of the boat.  Hope this helps. 

Thanks for the tip! I'll snoop around the stairs next time I'm down there and see what I find.

He is right on that is where they put the holding tank. I bet you did not get a survey. OHB thinks everyone does. Sometimes you can get away with it other times you get caught.

Had a 1975 43 nautaline and it never came with one from the factory, however my fathers 1974 43 came with one from the factory. I have the original option sheet for my Nautaline and the tank was an option back then, so if you see it discharging below the bathroom window @ the waterline and you don't have a Y-valve then you probably don't have one.