496 MAG HO water issues
 

I know this is an old issue but I have a question... Can the water drain system (actuator) on a 496 MAG HO in any way cause the sea water to shut off from the sea water pump? I recently changed the impeller and serviced the boat for the upcoming season and now I am not getting water to exhaust. The old impeller worked fine before the change because I started the boat to heat up the oil before I drained it. I only changed impeller for cheap insurance. I've tried everything in the forum... blipping the throttle, pulled and checked impeller rotation and condition, supplied lower presser on hose to muffs, and cracked bleeds downstream of pump. I am pretty sure it is the grooves in the housing (396 hours) but hate to change housing or rebuild it if it could be the actuator? I also know there is not an outside source (seaweed, rubber) blocking the flow since the old impeller was perfect and the pressure was good before the change. Any info would be fantastic!!!!

If it was the grooves in the housing then why did the old impeller work just fine? Are you giving it plenty of time to get water throughout the system so it comes out the exhaust?

Did you bleed the air out of the air actuator system?
Do you have water pouring into the bilge of the boat with the hose on?

This is one of the reasons I hate muffs. A fresh water flush connection directly into the line before the SWP is MUCH better. It sounds like you are not priming, and the scoring is the issue. With your totally dry pump and portions "south" of the SWP; you may not be able to prime the pump. It's usually NOT a problem, but sounds like such is for your instance.

I only use the Merc muffs with the wire that passes thru the water passages. They seal up well and I know they won't fall off. I've never in 15 + years not have them prime the system. If the entire system is dry, it takes quite a bit of time and water to get the system refilled to where water will come out the tailpipes. On top of what Sydwayz lists above, did you get the serpentine belt properly tensioned? It would have to be pretty loose though not to turn over the seawater pump.

If you have a DWP lower, make sure the nose is properly sealed off. This may seem obvious but I know several people that have smoked impellers because they forgot to do it.

Trace your sea pump inlet hose back to the transom assembly, there's a 45deg fitting, under the 45' there's a fitting that fails with Bravo's, it implodes on the hose and allows air to be sucked in when the upper unit is out of the water. I didn't find the problem until I rebuilt the sea pump.

You could change the fitting but for me in saltwater was pointless. I put a block off at the transom, put a transom mounted pickup to a sea strainer, replaced pump and housing without the air system and installed a water pressure gauge. It may seem over the top but I just got tired of water issues, salt water, shallow coves, sea weed, sand in the heat exchanger and so on...

Thanks for the replys...
First the way is see it the old impeller would groove along with the houseing and seal it up. The new pump would not fit into the grooves the same way and not allowing it to seal. I'm guessing thats the reason for the rebuild kits. Just my 2cents...
I tried to bleed it out in every spot I could and still no water...
The motor ran long enough to smell the exhaust bellows heating up. I did not want to run to long and damage them. I did however try starting it multiple times for extended amount of time and still no water. I do not have any water entering the boat from the acturators leaking. Not to familiar with the water bleeds and didn't know if the system lost or gaind pressure if they could move internally and shut off water to the pump?
I do have a set of the wire through muffs and need to try them next......

I have it taped but will check it again... thanks

There is a pull pin on the air actuator system. It's right next to the schrader valve (valve stem). When you pull that pin up, the white and green indicators on the top end of the air actuator system should pop IN with the air release. This air MUST be released before you try to run the boat again.

The Air Actuator systems does not replace the water in the system. The air actuators open two drain valves on the bottom of the motor, which allows water to drain out.

Yellow tag in this picture is the air release. Pull up on it. Indicators are right below it. They must be IN to run the motor on the hose.

[ATTACH=CONFIG]520281[/ATTACH]

VERY true. MUST tape off the other set of water pickups not being used.

start it and crack the throttle a few times on the hose, before I fixed it that's the only way it would flow, good luck

mercruiser has a service bulletin (2013-06R1) for impellers with part # 47-862232a 2 packaged from feb. 16 2011 thru may 30, 2013. the date is stamped on the front of the package. the impeller was manufactured below the minimum height requirement, causing pumps not to prime or making it very hard to prime.

ok thanks. I will look into it but I think the only fix is going to be either a rebuild kit or new pump. I was hopeing that valve may have something to do with it. Down here next to the Gulf of Mexico we don't "winterize" our boats. Really no need for the water drain system...

Anchor that is very interesting and I will check that!!!!

+1, thanks

The pump may well of worked with the old impeller as it would have worn itself into the grooves , this happened to me I changed out my impellers and motors wouldn't suck water , had to put in the stainless steel wear plates and bingo problem solved four years still running fine .

Get one of the rebuild kits with the stainless steel stamped inserts. Still think this is the most cost effective way to rebuild sea water pumps and I personally think they are better than stock once this is done.

If you have a sea strainer you may have to fill (prime) it first.

for a while over 2 years worth - Mercruiser had a lot of priming issues and overheat problems with the impeller out of tolerances for the Gen VII water pump. To find out if it could be your impeller pull the one out of the housing and buy a new one on the shelf currently from a stocking Mercruiser dealer because they should be totally cleared by now from those stocking dealers.

Take a caliper and measure to see if there is difference in your measurements. At least you will know that could be your problem. When I got the SB from Mercruiser I check all of mine on the shelf and had few to send back to Merc.. I posted this up here back then and here is more of the jist for anyone that might have interest. Link is below.

Good luck if you need more info just ask because during that timeframe we measured the impellers & hosings and always thought something was just hair off but how could that be Mercruiser is always right. Right.....

http://www.offshoreonly.com/forums/g...8-headsup.html

Just an update that I tried to JC marine kit on the 496. It worked great! It's like everyone said better waterflow than it's ever had. I was very impressed. The only issue I saw was the bolt that goes into the front of the snout behind the pulley gets a little tight. Other than that it worked perfect. Thanks for the help.

Yep. Worth every penny