I bought a crusader sd power pack motor http://www.1800runsnew.com/NLM/powerpack-NLM.html a little over two years ago and have been having problems with reversion the hole time. I've had the manifold and risers apart many times trying to solve this problem with little success. So I broke down and bought a set of custom made stainless marine manifolds and risers. The risers were made taller and longer to help stop the reversion but I think it was too late. With new exhaust I took the boat out for a ride and something just didn't seem right. got home and the risers off and still water so I pulled a compression test and found 7 cylinders at 190 to 200 psi and #6 at 145. I did a leak down test on #6 and sounds like air leaking through the exhaust. I will test the rest of the cylinders tonight. I guess I my question is what do I do now. Sounds like I need a new set of heads. Not quite sure where to go from here.

145 is normal.

190-200 is a 10:1 - 11:1 compression engine. Which, obviously you don't have.

Probably the high comp is from reading water in the cylinders as well. As the water takes up space in the combustion chambers - the higher you comp will be.

Was there water in the cylinder when you pulled the plugs?

I'm not sure if there was water in the cylinders the plugs were dry when they were removed. I do have marvel mystery oil in them now. When I did the compression test I removed all spark plugs and pulled the fuse for the ignition and fuel pump and cranked the engine until it stopped building pressure. I believe this is the correct procedure. I'll have to do another test.

Could the injectors be firing fuel and giving me a false reading?

If the plugs were dry, no water poured out the plug hole and there's no water in the oil, then chances care you aren't having issues with water in the cylinders.

Could the injectors be firing fuel and giving me a false reading?

I'd say there's a slight possibility that fuel could give you a false reading, but since you took the fuel pump out of the equation I don't think it would make a difference. You can relieve any fuel pressure at the rail by utilizing the shader valve, then run the test again to see if there's any variances.

Might want to pull that mani back off and retest your low one. Visually inspect the exaust port and seat with valve open and closed . On merc bumping yel/red wire turnes it over with no spark fuel. I have seen sbc vortec motors with aftermarket exhaust valves lose thier heads when subject to water .
Maybe crusader employs some juicy cam specs and requires specialized exhaust water dump -controls