OK... Finally... (friggin...friggin..frigin computers)..
First of all... if picture sizes are too big I apologize (I told photobucket to shrink 'em, but not sure if this is working)... Second of all... I should have been in bed 2 hours ago, so if any of this is gibberish I will figure that out tomorrow and and fix it then (if I have time... work is crazy right now).
OK... if this is the pooper scooper

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here's how it is set up on my boat. May not be able to do the exact same on your F25, but you might be able to borrow on some of the ideas. Also, this is how it came when I bought the boat... so I didn't create this - just dealing with what it is. Don't know how 'factory' or aftermarket the solution is.
This is long... but hopefully worth it to Larry and potentially others with the same 'old school' equipment.
Head Operation
The head has a built in holding tank (ie - the entire base). You prime it with about 3-4 gallons of fresh water, and add a bunch of toilet chemical (years ago T-5 Toilet Chemical was common (used it on my father's boat from about 1977 until almost 2000), last 10 or so years I have been using Liquid Gold, and since I couldn't find it last year there was some Captain Phab product I used instead).
PUBLIC SERVICE ANNOUNCEMENT : I am not affilitaed with Captain Phab in any way... but this past year has been the least oderiferous we have ever had with the boat... END OF PUBLIC SERVICE ANNOUNCEMENT
The chemical serves 3 purposes - i) deodorize things, ii) help break crap (literally) down, and iii) help break down toilet paper. The head works on the same principles as many RV toilets, so if you can't find chemical for it at marine places you can try RV places or stores that carry camping supplies. When you use the head, whatever you 'deposit' ends up in the (recirculating) tank. When you flush, the liquids in the tank are used to flush/rinse the bowl. Just after a fresh recharge, flushes are essentially 100% fresh water + chemical. The more you use it, the more diluted the flush fluids are...
When it gets full (or just too stinky - stinky may come before full in warmer climates than 'Canuckistan'), its time to pump it out. In total the recirculating tank holds about 5 gallons I think... so if you charge with 3 gallons you can add 2 gallons of 'human residue stuff' to it before it's full.
Charging the System
On mine the head is plumbed in to my fresh water "system" (white plastic hose leading to the chromed fitting and pipe). That just means that when I have to recharge it I have a simple tap to turn on (on the chromed pipe) to prime it with the 3-4 gallons of water (from my fresh water tank, which I can then easily refill as needed). If you don't have this tapped in to your fresh water system you can prime it by just dumping a couple of buckets of water into it. In the picture, the purely plasticized fitting and pipe are for the vent. Flush button is the little 'momentary on' pushbutton on the back left corner.
Draining the System
You haven't said anything about how you pump out or empty your tank today.... (which kinda creeps me out a bit!!!) There is a fitting on the back of the recirculating tank for a drain hose (I forget actual size, somewhere between 2" and 2 1/2" I think). In my configuration this hose goes out through the forward head bulkhead, through a hanging locker, and then under the v-berth. There I have an 'external' holding tank that holds about 15 gallons. Here are a couple of shots of it. Fat white hose that goes in the top is the line from the head... thin white line is vent.

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(Ignore the green stains underneath... that's the colour of the old toilet chemical. The tank fittings leaked a while back but have long since been sealed... and for those in Californ-I-A the white powder is something called 'Baking Soda'... being used here as an odour absorber and also telltale to let me know if the fittings start leaking again.)
The head itself has no way of pushing or forcing contents out and to the external tank. To accomplish this there is an external manual pump (similar to this
http://img.nauticexpo.com/images_ne/pho ... 256874.jpg) spliced into the hose between the head's recirculating tank and the external tank. The pump and its handle are in the hanging locker, so when I need to transfer stuff from the recirculating tank to the holding tank (because it's full, or just getting too odiferous) I crank on that for a minute or two. I have considered replacing this manual pump with a regular electric macerator pump, but so far am sticking with what I have.
I can transfer three full 'recirculating tank' fulls to the external holding tank before it is full. Then once I have a full external holding tank + another full recirculating tank its time to pay for a pumpout. Think we needed 2 pumpouts last year - and the second one was because the season was over and I don't store for winter without pumping out first!!!
At the base of the tank is a thick grey coloured hose - this is for pumpout.. and leads to my deck pumpout fitting.
Use
At the start of the season I prime the head with fresh water and fresh chemical. It gets used dozens of times without consuming any more water from the fresh water tank (because of the recirculating design). When 'its time'... I use the manual pump to transfer contents to the external holding tank. Then I recharge the head with fresh water and new chemical for the next cycle (and top up the fresh water tank if needed). When the head and the external holding tank are both full, its time for a pumpout. Pumpout sucks contents out of both the external tank and the head.... then I recharge the head and start all over...
For what it's worth : If/when this system 'craps out'.... I am probably going to replace it with a vacuflush system... but gonna milk this for as long as it keeps working (and/or I can repair it - 3 times so far, one of which was super-ICKY!!). 31 years and counting!!!