Thanks! I contacted SeaStarSolutions (Dometic) and they now sell this
SeaStar Solutions, which is designed for below the waterline applications and they guarantee a 180o turn in 4 inches(!) It replaces their 252 series hose. I got it at
www.go2marine.com, although it seems to be available in a couple other locations. I had issues with the SKU and images provided by those places so stayed with go2marine. I will report back my success or folly here in probably a week .... I so appreciate all the advice from everyone. This is a generous group.
That seems to be an appropriate hose for your application.
Hoses are not all that complicated. In general hoses should have a smooth bore, i.e. there are no ribs, bumps, or anything that would cause turbulence in the water flow or allow crud to be trapped.
Hoses that are used to suck, need reinforcement or they will be prone to collapsing and cutting off circulation. And by reinforcement I do not mean layers of some kind of fabric ply. One of the most common means of reinforcement is a (much detested) heavy spiral wound wire embedded into the hose. Other hoses, like the Trident Bilge pump hose has a thick prominent rib on the outside of the hose, the bore is smooth. Others, like some of the Shields sanitation hoses use a thick stiff material with slightly raised ribs.
The purpose of the spiral wire winding is to prevent collapsing from vacuum pressure caused by the pump. The material the hose is made of determines the flexing and bend radius. Take a look at the Raritan SaniFlex hose, it is wire wound and it is very flexible, however, the Trident 101/102 hoses are wire wound but not that flexible. The main difference is the material the hose is made from.
Unreinforced hoses are fine where the hose is pressurized, like on the downstream side of a pump. The fluid pressure will prevent the hose from collapsing. They are also fine for air vents, like tank vents.
Why is the wire in a spiral wound hose detested? Once you try to cut one you will understand. The wire appears to be a hardened steel wire that is exceptionally difficult to cut and cut ends cut skin quite nicely.