Could somebody tell me were the best or correct place to hook up a water pressure gauge. The boat has the gauge, looked under dash and there is a hose connected, but I cant seem to find the other end on the motor?????
Were should it be hooked up? There is a press. relief valve and a hose dumping overboard but I don't know what press. its set to. Thanks.

The intake manifold is a where we measure WP.

I second that. I run mine out of the rear of the intake manifold, but a lot of guys put them in the block drain port especially if they are running the 502mag mpi because the intake manifold doesn't have room for a port. I've seen some people drill and tap the t stat housing and put a -4 fitting in there also, problem with that being is you're seeing water pressure entering the engine not so much "in" the engine in my opinion. If you can't see it on the top of the intake check the block drain. Good luck.

Block drain will work just fine

Block drain works well until the sense line or sender gets plugged with sediment, just something to be aware of.

exactly