If you have sea strainers they don't always prime themselves. I have to fill mine with water the first start up.

Catastrophe:

The port the raw water is pouring out of is the air controlled valve that is used by the pump up drain system to evacuate the raw water when winterizing. Obviously it is stuck open or there is still air pressure on it from the pump up. Try releasing the pull air valve on the valve up at the fitting on the top left front of the motor that is used to pump the system up to open that lower valve. If that does not work you can try pushing a small screwdriver or something up the stuck valve opening and see if the plunger will un-stick. If not you will have to remove the valve and disassemble it and clean the corrosion or sticking debris.

Best Regards,
Ray @ Raylar

I passed this on.

Thank you very very much Ray.

Checking for pre-impeller blockage.

1. Does the (496 mag) hand pump pressurization expel pre-impeller or post-impeller sea water?

2. Does removing the blue drain plugs expel pre- impeller or post-impeller sea water?

3. If I pressurize my sea water system with the air pump, should I be able to force water into my outdrive and have the water exit passively into the bildge?

Thank you.

When you pump up the drain line and valve system on a Merc 496 you are supposed to be opening the pressure relief vales, one on each side of the engine. Depending on the year of the engine you are dumping raw water from both pre-raw pump and post raw pump. When you are removing the blue drain plugs on each side you are basically doing the same thing, except on the raw pump side one of the plugs will drain any raw water before the pump on the drive to engine inlet hose. The exhaust manifolds are supposed to drain over a slow period thru the check valves on each bottom exhaust manifold inlet fitting in the raw system when the raw system is being drained.

Best Regards,
Ray @ Raylar

Thank you.

I'm trying to (easliy) diagnose if there is an unexplained spontaneous blockage somewhere, before disassembling the sea water pump.

I only find one blue drain plug on the pump side, but maybe I'm not seeing far enough under the pump housing. (Very little space to maneuver; I'll use a mirror.)

Catastrophe;

I have the same problem on a brand new 2011 Formula, 496 Mag HO (sealed system). Water pouring out of the bottom of the waterpump from an untapped hole. What was the final conclusion to your freinds problem?