My forward tank is as you describe. It has two large fittings; one is the drop tube/pumpout, the other is the vent. As you noted, there are several 1" fittings but they seem rather small for actually dumping waste into the tank.
This tank is being returned to waste service from being converted to fuel when the boat was new so I don't know what the actual oem configuration looked like from the factory. But the large vent hose looks completely original. So per the factory setup does waste from the master and the bow head both get delivered to the tank via 1", 90 degree fittings?
The oem Hatt documentation shows "schematics" of the hoses going to the tanks but there is no line drawing or photo showing the actual connections/fittings.
First, are you having a problem with your existing tank not delivering the goods to the tank well enough? If not, then why mess with this mess? I will never be that bored. I've been there, done that (re-hosed the entire boat AND had to replace the fittings on the tank AND had to construct a new dip tube with a full-the-top tank) and I would never do it again just for the pleasure of seeing a larger hose/fitting.
Your two large fittings should be for the dip tube and the pump out, not for the vent. The vent should be a 1" hose. "So per the factory setup does waste from the master and the bow head both get delivered to the tank via 1", 90 degree fittings?" Yes. There is a tee where those two lines come together at the tank - a stacking tee as I recall (I'm not on the boat at the moment to to confirm)
As for the 1" hoses being capable of pushing the stuff to the tank, I can tell you that it's not a problem. As I recall, you have the Galleymaid heads, right? That mascerator grinds everything up so well that it's just watery substance that get pushed down that 1" hose. It's not pushing chunks beyond the GM mascerator. Even my Vacuflush is capable of pushing stuff down that smaller hose once it's been sucked down the 1.5" hose and flying around corners at 90 miles an hour which pulverizes it so that it fits into the 1" hose that it enters beyond the vac tank.
So, that leaves me wondering why you want to make the hose bigger, unless you're having a problem and even then, I'd look to my pulverizing equipment for a problem that has arisen after 30 some years. Also, check your hoses for that rock-like build up if you've had any saltwater flushing. The diameter of these 1" hoses can be significantly reduced - to the diameter of a pencil. Same with the 1.5" hoses which is how I found my GM pipes - reduced to 3/4" inside and that was BEFORE the stuff hit the mascerator, yet it was still flushing. At some point, that buildup will clog the hose/pipe and you just have to replace it, but not necessarily with something bigger.
