Advice please. 496 water intake blockage.
 

Please give me a logical solution check list. I am a diy guy, but not set up to pull engines out.

Engines were winterized last fall and fresh lake water was seen exiting each engine using the hand pump, and I also pulled the blue drain plugs. Engine temps while running are equal at 160F. Boat was stored in heated garage at 60F.

Each year I do the exact same pre-launch startup.

Before starting each engine:
1. Cooling system is de-pressurized and blue plugs are tightened.
2. House water is turned on (through a large diameter garden hose and exits a muff into the side intakes of the B1 outdrive) and it is splashing out the outdrive nose.
3. Through-hull exhaust is switched on.
4. I start the engine and within seconds water exits the exhaust tips.

Well today no water seems to be sucked into the port engine because none exited the exhaust tips (or out the prop area).

The port engine does not seem to be pulling water into the engine when started. (Starboard works fine and throws water out the exhaust tips as expected.)

Where is the most probable blockage? And how do I systematically solve and repair?

2004 496 mag. Never a single issue with either engine since day one; original owner.

Thank you.

Sounds to me that you may need a new sea water impeller which is on the lower portion of the engine starboard side. I just changed a couple on my 496 engines-- Not a fun job. Good luck!

The same exact problem I had today. Last spring I put new impellers in but did not replace the housing.

likely the impeller
 

Thanks. I think you have correct diagnosis. Is there a way to be sure before I begin disassembly?

And should I do the starboard impeller as well, or will a new impeller be as likely to fail anyway?

Also, any chance you have a list of 'recommended' additional parts to replace, or just the impeller only.

housing too?
 

So are you saying the housings are junk too, and should be replaced as a matched set with a new impeller?

If the housings have any grooves in them they're junk.....i changed my impeller and it won't flow enough water now...

Sunsational: If you haven't changed the impellers in 7 years you are long overdue. Of course, change both. You won't know the condition of the housings until you get them apart. I purchased Globe run dry impellers--allegedly better than Merc.......

Quality Impeller/Housing combo
 

Literature indicates the Globe impeller is likely superior. Globe lists part #2000 as the only impeller for a B1 with key. Besides a new o-ring seal, are there any other parts I should replace at the same time?

Is there a higher quality housing out there as well?

I might as well replace both on each engine and perhaps last another seven years!

Thanks for information.

Remakable you guys are talkin about this engine. Went out with a guy today with new 496 that he just received from Baja 4 weeks ago.

He started it up and water was pouring out of a verticle hole just below the two blue drain plugs. Is that hole supposed to be plugged ?? I have no knowledge of that engine.

Its the long weekend and no one is open to ask.

I'm guessing and only guessing that Fountain sent it up here winterized or something like that.

The hole where the water is pouring out doesnt appear to be threaded.

The pumps brass little sand, junk someone in arizona makes a nice rebiuld kit ,R&R industries with stainless plates ,great improvement .

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.

Anybody know?
 

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

Thanks, 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?