My vent is still original and has the screen on it, I know about the upgrade to 1" and remove the screens, but couldn't figure out how to remove the chrome vent from the hull to remove the screens on them. Any advice or recommendations?
Use a screwdriver blade, pliars or whatever works to knock the screen loose.
It's not hard to replace the vent thru-hull with an open bulkhead thru-hull. You need to remove a thru-hull from the INSIDE of the hull. There's a nut on the threaded barb..remove the vent line from the the thru-hull, then back that nut off the barb...you may have to scrape some bedding compound out from under it. Push the vent thru-hull out (there may be bedding compound under it on the outside of the hull too)...stick the new one in...apply new bedding compound on both the inside and the outside...tighten the nut, put the hose back on the new barb...you're done.
One more thing: You said, "Realizing at that moment the holding tank must be higher then the head I managed to raise the hose above the toilet and the water flow slowed".
To do it right the toilet discharge line really should go straight up immediately from the toilet and rise high enough to be just barely above the top of the TANK. That'll require a loop--not a vented loop, just a loop--in that line. This has a couple of advantages: You only have to pump the toilet long enough to push bowl contents over the top of that loop, gravity will get it the rest of the way to the tank (replacing the joker valve annually will ensure that the toilet has enough "oomph" to do that easily). If you learn to follow bowl contents with a little clean water to rinse behind 'em, then use the DRY mode to push that over the top of the loop, there'll be less than 1/2 cup of water to run back to the toilet, plus you'll increase the number of flushes your tank can hold by 50% or even more.
I'm not sure why it would ever be necessary to let ANY water run out the hose (what hose??) to the shower sump until it is empty next time...Is the backflow enough to overflow your bowl?? 'Cuz only the amount of water left in the line between the toilet and the tank can run back to the toilet...and that's not nearly enough to overflow a bowl.
Do you have my book? The title (my publisher's idea) is a bit misleading...'cuz although it does deal with every source of odor on a boat and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em.
--Peggie