I would like to thank everyone for the great input! We have now cleaned the bilge
area with bleach water and tried to air it out as much as possible. We can see 95 percent of the hose runs and bilge
area it all looks nice clean and white now.
We have also filled the holding tank
with fresh water and pumped out several times. After several fresh water flushes we filled the holding tank
to the point water came out the vent line, it appeared to be completely open. Also with the holding tank completely full of fresh water I checked carefully for any leaks
around connections. The tank was then left with several gallons of fresh water in it.
I realize that the holding tank was probably lying for a very long time in a anaerobic state and also am sure the old hoses were permeated. We have had to leave the boat for a few weeks . Upon return we will try one of those tank additives to try and get aerobic action going. (Or better yet get someone from the marina to add it sooner)
We are now fresh water flush with our new head so that should also start to help. By the time we left the boat Sunday we were starting to think the odor was lessoning. As bad as the old hoses smelled it seems logical that they would have left odor behind.
In a new set of hoses with good connections it would seem to me that even if your tank is anaerobic that the odor would be confined to the inside of the tank and to the end of the vent line. Is that correct? I realize we want to get the tank aerobic at any rate.