welfare racing

I have supercharged 540's with cross overs, there is not recurculation pump so the mercruiser water pump is supplying the water for the system

I added water pressure gages, they are hooked into the block (where the block water drains are with AN fittings, normal locations)

Im using gaffrig water gages (new and were sent back for rechecking to be sure they were good, and brand new)

At idle I see 0 pressure

At 3500 and up it goes to about 2.5 lbs and that is about it

there is more than enough water and the engines dont over heat even at WOT still shows 2.5#

so the question is how do I make the gages work .... or read so that I know that there is good water flow (as at below 3500 RPM it shows 0)for the visual as I am running to be sure I dont burn something up if something gets picked up

Yes the impellers are good

Thaughts?

compedgemarine

they are not flow gauges, they are pressure gauges. that is what the block is seeing for pressure as are the heads and everything else. most likely you have too much area for water to exit the tailpipes so you have lots of flow but no pressure. how does the water exit the pipes and can you restrict it slightly or close up the opening a little to bring the pressure up?

endeavor1

iTrader: (3)

That’s exactly how mine were setup and I never had pressure indication problems unless the pump was failing. Few things I would check: ensure the line for the gauge isn’t kinked anywhere and also no debris have plugged the lines. Another spot I have added them too was on the oil cooler of a 525efi. There is a sending unit already there so I just T’d off of it.

Tractionless

I have mine hooked into the thermostat housings on circa 1996 7.4 LX MPI's. From new (water pressure gauge kits) I have 2 psi at idle and no more than 10-12 at WOT. Same with new or 2 year old impellers and everything is OE. Can lay hands on risers without issue and temp is never over 150* in Florida summers.

Griff

Seeing 0-2 psi at idle is pretty normal. Usually with crossovers, people have problems with too much water pressure.

The water pressure gauge I had connected via the block drain on my Pantera got clogged all the time.
The ones I have in my AT are in the T Stat housings and have never clogged in 12 years.

The first thing I would do is pull the hose at the block drain and put 20psi of air pressure into it and see if the gauge(s) reads 20 psi.
I have to wonder if the tubing for both engines is kinked somewhere.

endeavor1

iTrader: (3)

I usually see around 10-12 at idle and low to mid 20s running on my smartcraft and mechanical gauges. The other boat I added gauges to read similar. Griff is spot on, reading off block drains usually made it so I had to clean the lines out once a year.

Pismo10

You want lots of flow, pressure not so important. Pressure often indicates outflow obstruction.

compedgemarine

yes but without any pressure it will allow air and steam to sit in places causing hot spots and it will not be forced out. that is why they want 10 to 15 psi when it is up in the rpm. from the sound of it he has plenty of flow but almost no pressure up and running so he needs to restrict it at the last point of exit to bring it up some. that is why I wanted to know what set up he has. right now it is all a guess as we dont know how the water exits or what size any thing is.

BUP

iTrader: (9)

What engine and where are your pressure sensors located ? What set up are you using to monitor water pressure ?

28EliminatorDave

I Was Having The Same Thing On My 502, Its Pro charged So No T-stat. I Bought A Restrictor To Install Where Thermostat Goes But I Have Not Installed Yet. Theoretically Pressure Should Rise A Little