I am having an issue with two Procharger M1SC's. Started this spring on BOTH motors (500 efi's). I am not developing any boost on either motor. I can only run the boat up to 4500 rpm and I'm at zero boost on both gauges. Normally I would start to see some boost at about 4000 rpm and it would run up to approximately 5400 rpm @ 5 psi boost. At idle both before and after the chillers I have good air flow. I have replaced both belts and made sure they're tight. I've run a separate air line to the intake with a remote gauge and still see 0 boost. I'm at a loss as to how this is even possible on both motors. All I changed over the winter was new distributor caps, new plugs and changed the oil in the Prochargers. Anyone have any suggestions of where to start looking?

Do the Prochargers spin ok by hand? Are the blow off valves stuck open?

Yes they spin fine by hand. I don't believe there are any blow off valves on these units?

When turned are the vanes spinning too?

Wonder if a hose was taken off somewhere during winterization and wasn’t put back on.

Any chance the keyways are missing in the drive pulleys

I haven't checked that but I will. I'm assuming they are bacause at idle its definitely pushing air thru the intercoolers

There is only one discharge coming off the Procharger going into the intercooler. No other hoses.

I pulled the pullets off and checked the keyways and they were fine.

you should have other hoses on the engine that’s someone could have off off to fog instead of putting 2 cycle oil in the water separator. If they forgot to put those back on you would have a boost leak.