Hi Guys. Did a search but couldn't quite find what I was looking for. As title says I'm adding water pressure gages to my 500EFI's and wondering where is the best location to tap into the cooling system.
Also what would be considered "normal" pressure at say cruising at 3000 rpm?

Thanks!

Many tap replace a drain plug with a threaded barb

The pressure depends on a few things: are you using stock bravo pickups? Transom mounted? Relief valve?
15-25 PSI is usually a safe bet for WOT and a good pressure to aim for

The previous owner converted the water pick up from the drive to transom pick up and yes the pumps are just the stock ones that come on the 500EFI.

I connected to Tee fitting on port side of block with mechanical gauge, 1/8 inch tubing

Cold idle close to 5 to 6, once thermostat opened would see 2 to 3
Cruise (36 to 3800 rpm) around 25 with new impeller, WOT a bit more

509 MPI, bravo pickup and Merc pump

As others have said…we use drain plugs on block.

Thanks all. Gages are still being shipped and include the polyethylene tube. Didn't realize the pressure was as high as mentioned. I assume the hose uses a clamp to the barbed fitting? Definitely wouldn't want that line to blow off. Was thinking those shark jaw type fittings used with polyethylene plumbing may be the ticket unless screw style clamps are sufficient.

I used 1/8 inch air brake line with brass compression fittings. No chance it will come off

Yeah that's a great idea too!

On my old boat it had the reading taken from the block drain, it would constantly clog.
On my 502mpis, the fittings are in the T stat Housing. Never had a clog in 16 years. The TStat housing or intake manifold are better locations IMO.

You should see 1-2 psi at idle, 10-20psi at cruise rpms and 20-30psi at WOT

mines like this with a -4 fitting on a rubber hose headed to the dash