Re: 1978 500 water pressure
If you can, try and locate a 0-15 gauge. They do exist, I just installed one on my boat a couple weeks ago.
With the 0-30 gauge you will hardly see any movement in the pointer. As Ed pointed out in his post, you will most likely never see the needle move above 1/3 scale on the 0-30 gauge. Even at WOT you will only achieve 10-12PSI at best. At idle or no-wake speed the needle won't hardly move off the peg.