I don’t have any sanitation hose leaks, but a lot of fine cracks on the outside of the black hoses, especially where they bend. I am getting head order from some of these locations. Not horrible yet, but I am not waiting any longer.
10 years is about the average working life of ANY hose, so it's definitely time to replace your hoses...although I suspect that at least some of the damage to the outsides of radii in bends was done by heating the hose to make it bend tighter than it wanted to which stretched the "skin," weakening it enough to cause it to tear. If you'll have tight bends in your new hose, do NOT heat it to bend it...instead, break the hose and insert inline radius fittings...or go with a hose that DOES bend enough (more about hoses later).
We have two electric macerator heads with discharge lines that are 1” coming out of each one.
Sounds like you have Jabsco toilets....they're the only mfr who uses 1" discharge fittings. 1.5" is the standard size that every other toilet and tank mfr uses. So if you want to eliminate the reducing adapters, it would be a simple matter to replace the 1" discharge fittings on them with 1.5" fittings, available directly from Jabsco. Specify whether you need straight or 90 degree fittings, regardless of what you have now...'cuz all toilets ship with straight fittings when a 90 is what's really needed, which can make for some serious plumbing problems and leaks. Give Paul Campagna in tech support a call: 978-282-5246.
Whether to eliminate the y-valves and flush only into the tank depends on where you plan to cruise. If you're planning to do some ocean cruising, you'd certainly want the ability to flush directly overboard...but if you'll spend most of your time in US coastal waters inside the "3 mile limit," you can prob'ly do without the ability to flush directly overboard.
However, 15' is a very long run from the toilet to tank. About 6' is as far your toilets can move bowl contents in the time most people will keep their finger on a flush button without a lot of help from gravity...so unless it's downhill all the way, that could be a good reason to keep the y-valve in the discharge line, relocating it to a location that puts it higher than the top of the tank.
If your overboard discharge pump has been sitting unused for more than couple of years, it's prob'ly deteriorated to the point where it's unlikely to work. So depending upon how far "down the road" it will be before you can use it, either replace it or remove it altogether (it's easy to install one when you need one)
About hoses... this is NOT the place to skimp on price! Cheap hoses will permeate in a heartbeat. There are only two I recommend: Trident 101Trident Marine: Sanitation Hose
is a double-walled rubber hose that's been on the market for about 20 years without a single reported odor permeation failure. It has only one drawback...it's as stiff as an ironing board, so not the best choice for a system that has a lot of bends tighter than very gradual sweeps. About 6 years ago Raritan introduced their SaniFlex hose Raritan Saniflex Hose
...flexible enough to make a U-turn. Pricy, but not single reported odor permeation failure either.
If you'd like a little one-on-one help in spec'ing out your plumbing runs, you're welcome to give me a shout...I'll be glad to help you.