Originally Posted by kjzerr
....I thought I am really out nothing if it doesn't work in the long run. Worst case, I will have to eventually replace the tank with a rigid one that will fit in the same compartment......
This is true, with one big addition. Not working out means it might smell horribly. The thought of remediating a used holding tank is one of the least desirably boat jobs of all time. Therefore, you will find you have to live with that terrible odor until you have the time or desire to deal with it.
Ask me how I know...........
A tip. Be absolutely sure there are zero low spots in your discharge lines and they have a desire to dip when full. They need to empty fully into the tank. If waste sits in them, they will begin to stink and you'll have to replace them too. No way to repair a permeated waste line.
It wasn't clear whether you will have a vent line. One want one to be 1" or larger. There is absolutely zero chance of success without one. The boat will wreak without a properly vented tank, as the odor is directly from anaerobic bacteria. On the other hand, keeping it from clogging and effectively not having one, is going to be a trick.