If the hose is clamped at the inlet side leading to the engine from the pump, I'm having a hard time beleiving it'd blow the hose off, first of all!

What pump is this? Sounds to me that it's probably a Jacuzzi YJ or a Golden Eagle. Gotta be something seriously plugging the bowl or wedged in the nozzle. plastic shopping bags, something......have you pulled the hand hole cover, and new gasket BTW, that you say was spurting water?
No way should that kind of pressure be coming out that 1/2" pipe tapped into the bowl for engine cooling. FIX the problem, don't band-aid the result........
I'm a fan of pressure releif, since we run much hotter engines, cams these days, and build our pumps to much higher standards than they did in the 70's and 80's, but still, there is NO WAY that pump should even be capable of throwing that kind of pressure through that tube unless something is seriously wrong in the bowl or nozzle area.
Just my .02
Ray