502 mpi fuel pressure( how to check)
 

before and after installing an adjustable fuel regulator

There is a shroeder valve on the fuel rail, hook a fuel pressure gauge to the valve and you will get your reading.

I posted this answer yesterday, but it was lost in the cyberworld.

As RonS said, there is a shraeder valve on the front of the fuel rail under the intake plenum. It is a little difficult to get to, at least mine is with the closed cooling system, but it is possible. The other alternative is to use the fitting in the back of the fuel rail, directly in front of the distributor. There is a 1/4" pipe plug there. Remove the plug and attach a guage. I was able to hook up a permanent guage by using the rear tap.

Hey liquid,

Ever get your miss figured out. What was it?

Ron

I think it is in the plug wires or cap, still missing occasionally

Checkmate454mag
You mentioned having closed cooling system. I don't here of that system too often in performance applications. Could you describe what you have and any pros or cons? I am in salt water all the time and have always thought closed cooling would be the way to go if you can dissipate enough heat. How's it been?

Re: 502 mpi fuel pressure( how to check)
 

Once you get the gauge hooked up, there are two ways to check the pressure:

1. Easiest way: Just turn the key into the on position w/o cranking the motor. While the fuel pump is running, look at the gauge to check the pressure. It will drop about 5psi when the fuel pump stops running. The correct reading is while the pump is running. Turn the key off, make your adjustment, then turn the key back on and watch the gauge. Repeat as necessary.

2. Crank the motor with the vacuum hose disconnected from the adj. fuel pressure regulator. Plug the hole in the regulator (where the hose was) and read the gauge.

Be sure to relieve the pressure from the gauge before disconnecting it.

Just like ths rest has stated. I would check it first and then install the regulator. It is kind of a pain getting it set right, because a small adjustment makes a big change in pressure and it is not that easy to hold while tightening the nut. Just have to mess with it a while.
Good luck!

Seamate ...

I think the others have covered the original question here but maybe I can address yours.I have a 502MPI with the FWC option and have so far been surprised at it's cooling ability.In the height of summer here the water is about 88 deg F and air about 87-90 F with humidity fluctuating between 75 and 90pct.Engine temp runs around 190 max... same in the winter also.Unfortunately merc does'nt make a 'full fresh water cooled' package so the lower half of your exh manifolds will be raw water.The sea water here (no lakes etc.) is so salty it's more like acid and FWC is a major plus for the engine and good for resale value too !

Seamate;

As Madbouyz has said, the system works great. I have had no trouble at all with it. It has been on the motor since new. I have about 230 hours on it so far. The heat exchange mounts to the front of the motor. It requires almost no additional room forward. As was stated, the manifolds still have salt water in them. The raw water gets pushed through the heat exchanger, then to the manifolds( cooling them), then dumps through the pipes. I have the Mercruiser system, it fit perfectly. The whole job took me maybe 2-3 hours. See attached link..

http://www.mercruiserparts.com/Show_...COOLING+SYSTEM