496 MAG HO water issues
03-14-2014, 09:14 AM
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03-14-2014, 09:17 AM
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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!!!!
03-14-2014, 09:18 AM
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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...
03-15-2014, 10:00 AM
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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 .
03-15-2014, 11:35 AM
#18
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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.
03-15-2014, 02:23 PM
#20
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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
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
Last edited by BUP; 03-15-2014 at 02:39 PM.
