I currently have my 72 stardust Cruiser in the dry for a bottom job. The boat has three discharge outlets that are either under the waterline, or right at the water line. I'm thinking about having all three outlets welded over and put everything (head, shower, sinks) into the holding tank. I have slip pumpout so this is not an issue. My thought is that closing off these outlets "could" prevent taking on water in case any of these outlets ever rust through.

Thoughts, comments, and advice?

p.s. There's only two of us that stay on the boat (weekends), pretty good size holding tank, and pump out is easy.

Go ahead and do it but your grey water outlets are above the water line and legal in most areas. You may be underestimating the amount of grey water you generate.

I would have sworn that all three outlets were below the waterline.  Two Starboard and one on the port side.  I know for a fact that one of the outlets on the starboard side is below the waterline, for the head.  The other is a much smaller outlet, about a 1/2 inch diameter.  Was thinking the smaller outlet was for the shower.  The one on the post side is the same siaze as the head outlet and very low on the side.  Maybe I'm wrong about these....  wish I had paid more attention prior to pulling the boat out and pressure washing the sides.

If these have seacocks (Valves) on the inside to shut them off then you shouldn't have to worry about them sinking your boat. Just shut off the seacocks.

Are the y-valves associated with most marine waste systems also illegal in most states or are they allowed if turned off so as not to discharge directly into the water? I have turned mine off (holding tank position only), removed the handle and discharge hose and plugged the valve. To do anything more would mean hauling the boat and I do not want to do that.

Ken, with the seacock turned off and the handle removed, you're fine (and legal).  The law says that the valve must be turned off AND SECURED.   What you've done, more than complies with the law.

Sailer, I thought you had a type I MSD. as well as a III holding tank? In the waters where you are you can discharge trated sewage which is actually better than pumping taking to the sewage plant and them discharging back into the water. On reflection seems I remember long ago you did not want to do that. So I guess you do not have a type I. You can lock the head and be legal, you can have a bucket and technically be legal as long as you do not dump it in the water. We do not have all this mess down here. I have repeatedly said those with type III holding tanks will dump when no one is there. That is what many do.

I have two electric heads with macerators and a 50 gallon holding tank. It seems to work ok as long as the on shore bathrooms are used in the marina. Fifty gallons seems like a lot but it fills up in a hurry, especially when the women are on board (gonna get slammed on that one). I don't think I have room foranyother kind of system unless I do some major remodeling which is out of the question. We've done enough remodeling and it is time to have fun, if we can afford to take the pig out of the slip. Pretty nice cabin on the river.