Re: Diagram of poppet valve assembly
I spent some time understanding the son's '95 150 and I agree with the diagram.
From the back of the engine the hose coming from the top of the block goes down to the poppet I am going to have to assume as I didn't explore that part that much; but I saw the hose and where it went. I'd have to assume the popoff is located on the bottom of the block in the back with this hose going to it per the diagram.
The stats are on the top of each cylinder bank and off the cap covering them there is a series connected 3/8" hose going from starboard to port then down below the engine and discharging into the mid section; additionally, this line tee's roughly half way down via a 5/16 hose to the pee spiggot.
With this arrangement, you will not get any pee till one or both stats open. I didn't like this and put the pee on the tube coming from the top of the block. That way I get pee within about 30 seconds of startup rather than having to guess that I have water till the stats decide to open (143F).
If, in fact you believe the diagram, and I do as I said, you do not get any water (to speak of) out of the powerhead until you either unseat the popoff or the stat(s) open.
I believe this as you need pressure to keep the block full of water so that the upper cylinders are surrounded by water. If you notice the little vents in both the stats and the popoff, you have a small amount of curculation prior to either function functioning. Part of the reason for this (I'm sure) is to keep some water running through the exhaust manifold so that it doesn't overheat.
The popoff is supposed to unseat at around 2500 rpm (need that rpm or better to get adequate pressure from the water pump) or when the boat is moving forward fast enough to provide comparable pressure on the water system via the water inlets in the lower unit.
From what you are saying, I'm going to say that your popoff is either missing or stuck open.
My best guess.
Mark
