Here's my two cents (what my advice is usually worth):

1) The city water line coming into a houseboat is what size? 1" diam or 1/2"? I plan on using a pressure regulator and a check valve (is that a good idea?) then have the line go into a manifold which will re-direct the smaller water lines out to other faucets. I will of course use an internal clean water tank for long excursions which will have to integrate in with the system.

The connections I've seen use a standard water hose that is 1/2 " ID. A pressure regulator is ALWAYS a good idea--some marinas have astronomically high water pressure to get enough of it to the many slips. Don't use the internal tank for drinking water unless you thoroughly clean it out and sanitize it (and I still wouldn't use it! We carry fresh water with us for that purpose.)


2) How is venting of the bilge and inside done? using a blower to get air OUT or such clean air IN?


There are forward facing ducts that shove air in as you go along. The blowers (two) pull it out and should be left on at all times. Be sure to check the hoses on those blowers: Mine had fallen off the outlet grill and were merely recirculating the fumes!


3)I'm going with a propane hot water heater (propane locker on a shelf/bracket off the stern of boat--OUTSIDE of the boat) any ideas on good companies that make a marine grade propane hot water heater?

Don't know anything about them. Sorry. The wife claims that enough heat remains in the electrically heated tank for a shower next morning. Me? I freeze to death!

You'll find that Marinettes have few vices: No rotting wooden framing, no split and leaking deck to hull joints, etc. The CAPAC meter needs to function properly, and YOU need to maintain the anodes in the .90 to 1.2 volt range.

Jeff

I used PEX tubing and push on fittings to hook up my water heater. That stuff is great and you can get ready made manifolds. All you need is a tube cutter and you are a plumber.

Wow, I guess people do respond to these forums! Thanks so much for a wealth of advice (plus the 2 cents:-) Computers are a wonder, but I have a lot to learn...as I do with this project houseboat I got myself into. I've though long and hard about going with propane for heating water. The main reason for propane is due to my boat being located away from an electrical source maybe for long periods of time. I have the propane in a custom made aluminum locker box that is to hang off the back (on a shelf-like bracket.) I also have another shelf/bracket on the other side of the stern/transom which is where the generator is to be located inside another enclosure special made for the generator. I wish I had found this forum earlier. I am leaning towards the Pex tube and fittings along with the manifold diverter. My question about the venting is so I can get those in there so I can start "drying in" the boat and get it rain proofed and hopefully start the process of getting it painted and finally in the water (it has been on keel blocks since 2007 when I got it.)

I think I saw those regulators at Home Depot. I also saw what looked like the Pex tubing connectors/fittings. I will compare the specs on what those fittings are made from. I may over kill it and go with a stronger material since it cannot fail or break. About the vents though, I have: 2 bow area vents, a vent on each side of the superstructure, and 4 vents for the engine room/area. Note: I have no engine in there since I've gone with an outboard (it is to be a storage area.) Do the side vents and 3" vent tubing just hang down into the bilge or does it have to be on some powered vent blower? I may have the engine bay vents on a blower.
The vents that were in there before had a plastic ring that fit inside the hole. That ring is what held the clam-shaped vent in there, and there was a venting tube that looked like dryer duct about 3 or 4" diam. (but those vent tubes were long deteriorated away.) The problem is: that plastic ring in no way waterproofs the vent hole area. The plastic ring has weathered and warped. My brother does drafting on auto-CAD and soon I may ask him to draw up a good rendering of what I intend to do as well as pictures, but where do I send them for viewing?