New impeller won't pump water. ARRGG

TikiHut2

Briefly ran my 5.7 merc at idle in the shop after installing a new impeller with my muffs attached but there's no water flow at the exhaust. Shut it down after 30-60sec and I'm stumped. wth

I took pictures of the intake and out-flow hoses to be assured that they didn't get reversed and reattached them exactly the same after pulling the brass seawater pump and replacing the old impeller with a new one. Pic of the belt configuration confirms it went back on correctly too.

 I had to detach a hose that runs under and around the pump then back up to the engine water circulating pump too but also re-filled it with water before starting the engine. Even pulled a hose off the exhaust riser and ran water from the hose through it until it filled the system and came out of the gimbel housing at the exhaust. Restarted with the muffs and water hose set at 60psi of water and still no flow through the pump. Luckily I greased the new impeller pretty well to get it in the housing or it'd be toast.

Any clues? Do I need to prime something I'm missing. This ain't my 1st rodeo so I'm humbled to even post this but I'm at a loss. Mike

212rowboat

How long since you ran that thing? It may not be your raw water pump, just as a suggestion.. pull your 'stat, and try it again.. if your stat blade doesn't have a couple vent holes, consider tapping some in it.. I prefer three of them, about as small as you can find in diameter, at noon, four, and eight o'clock .. a good bit of air trapped in the block unable to purge can and will stop circulation in its tracks.

212rowboat

I kinda thought that through after posting... even with a 'stat stuck and w/ air in the block, the neck bypass thingy would allow flow through the system, just not the block.. the block would just gurgle on what juice it did have, sipping off the circulation pump bypass, and releasing it if/when the 'stat opened..

TikiHut2

Went out before dawn(before i saw the addl posts) to pull the stat and drill 3 tiny 1/16" holes but after doing that I came to the same conclusion that the seawater pump exits across the thermostat housing AND through the water assy under/around the engine then out the risers.....which it still fails to do AT ALL, nothing, not a drip even though I'm forcing water to it at 60psi. :-?

There was a very slight amount of wear on the back part of the pump when I took it apart(pix) but I wouldn't think it's enough to totally impair the pumps ability to prime or even pull what I'm forcing toward it. The other impeller was working well but was 2y/o and although still in one piece, it'd started to loose it's flexibility. When I reassembled the pump, the new lightly greased impeller seemed to fill the cavity completely but I didn't Mic the two parts looking for a .030" difference. It was certainly a seemingly good fit with the lid pressing it into place.  It came from our local top-tier multi-million dollar merc/searay parts/service/dealership who should certainly track recalls and update their stock. BUT if it'll happen, it'll happen to me on Halloween I guess.

There seems to be some sort of check valve looking part in the raw water assy down under the port side manifold(pix). Could this be stopping the flow even though I've primed this thing from every orifice I can cram water into or am I grasping at straws. I'm stumped and would hate to pull it again if I'm missing something obvious but it's not horrible if I need to, just unbelievable.

Here's a pic of the OEM parts bag (mfg date 3/13?) for my brass seawater pump on our Mercruiser 5.7 MPI Engine# OM673418 (is this a recalled lot?), the pump and backing plate pix, and the ck valve pix?
Thanks Mike





(orientation is screwy. this actually under the port side manifold)

Black_Diamond

Check valves are evil creatures, they sound like a good idea but have bad habits of getting stuck (usually open though).  Debris, corrosion, wear, etc.  Plus they restrict flow

Even if your pump case was worn, you are pushing in water underpressure from a hose I assume, so I don't think it would have to work hard to prime in that case.  What if you ran the water with the hose disconnected to the input side of the pump, then you would know if you had a blockage at least and narrow down where to look.  Just a crazy thought.

>-

TikiHut2

Thanks BD, Yeah that ck valve (if it is) has two SS bands pressed on it so it'd have to be cut out and probably replace the hoses that would then be too short. Not fun or real practical without pulling the engine.

To get a hose right at the pump I'll have to pull the pump and adapt an in-line fitting but would only be bypassing about 3' of inlet hose between the drive intake holes and the pump inlet. I suppose I could splice in a Perko flush valve to use if I ever want to flush it at dockside. (AMAZON PERKO LINK)

Sounds like I'll be pulling the pump again to get a hose on the drive and see if it's a supply problem anyway. I'll also probably bypass the pump and adapt a fitting to the outlet hose and see if 60psi of hose pressure will run through the system unimpeded. That'd narrow it down to the pump I guess. Dam# gremlins. Frustrated Mike

BoatAway

the fins at 12 seem to be more compressed than the ones at 6. is that right?

I'm planning on doing this to my engine this month too. good luck!

comm1

that is how the pump is able to pump water, it picks it up at 6 and compresses the water at 12 

TikiHut2

Well another early morning call to remove the pump and....Lucky me it looks like I got one of the short impellers (pic). New on rt, old on left. You can see where I might not have caught the difference. A big thanks go out to Merc, but especially my local dealer who didn't check their inventory. :!! Really???

The good news is that I can get the pump out in under 9mins now, beginning to bench....not a talent I really wanted.

I'll definitely check for water flow on both sides of the pump later today before I put it back in. The plate is slightly grooved and I considered having it milled by about .030 back to new but we'll see if I can find somebody to do it. $350-$450 for a new pump motivates me to try.

The intake hose is oriented on top and the outflow is bottom as confirmed by the handy pics I have from before the disassembly. Thanks a lot for your help and I'm trying to effectively document my problem so somebody else might benefit from the resolution. Thanks again, Mike

Black_Diamond

Tiki, might be worth looking at the SS upgrade pump that was posted a bit ago?

Glassguy54

OUT IN 9 MINUTES?!! WOW!!! How were you able to accomplish that? Can you post a pic or two of your engine compartment and pump location? Do you have the Gen3 cool fuel module? On my 2007 246 (also 350 MAG MPI, B3) things are so tight I'm not sure if I could do it in 9 hours! I even removed the water tank to give me slightly more room, but still....

TikiHut2

BD, Don't remember seeing a ss pump. Is there a link?

I can get to mine pretty easily. Getting the right tools and sequence make it an easy job once you do it once......and then immediately again like I had to do.

Black_Diamond

http://www.hardin-marine.com/p-15774-stainless-steel-gen-7-sea-pump-for-mercury-350-496-and-502-mag.aspx Here you go!

TikiHut2

Thanks BD. Interesting alternative

BoatAway

wow. that'll probably last many engines lives!

TikiHut2

Went back to the dealer and every one he had was about 3/32" shorter than my original and all were mfg within the recall period of 2/13 - 5/13. Will call merc directly to see what to do. May end up with a new pump

TikiHut2

Al said earlier "How's the backing plate? Any Grooves?" Well aside from the short impeller that he also mentioned (and I inadvertently installed), the backing plate is showing some slight grooves that a new impeller (short or not) might not fill causing a lack of prime.

Looking on the net for new bronze pumps is shocking but I ran across a machinist who is selling a CNC cut 1/16" SS backing plate upgrade for these bronze pumps on Ebay at a fraction of the pump replacement cost. Might be a good upgrade for a very expensive but virtually disposable pump once it's a bit worn or simply needs a new impeller that won't align with old wear zones.

(EBAY LINK TO PLATE)

How is the housing?  any grooves?

How is the housing?  any grooves?

How is the housing?  any grooves?

Black_Diamond

Looks like an interesting solution.  It use two o-rings to seal then (both sides)?

TikiHut2

Thanks Al, Just heard from Merc in WI and they want to exchange my seawater pump at no charge if Ill send my old one to them so they can investigate why the green dot certified recall impellers are still so short.

THATS AWESOME CUSTOMER SERVICE!

I pick a new pump body assy tomorrow and they're expanding the recall so no one has to experience my frustration. Thanks I owe you one, as does everyone else who wouldve hit one of these.

Mike

Black_Diamond

Wow!  Sweet deal there.

TikiHut2

Positive attitude was definatly the key. Never pressed just offered to help if I could. I said I'd send the old impeller at my cost before I heard they wanted to give me a new pump for my trouble.

Couldn't be more relived. Put a water hose on the disconnected intake and outflow engine hoses and everything flowed like Niagra Falls so a new pump will fix everything.

Black_Diamond

Double win there Tiki. Congrats

frodo13056

Al, I seem to recall that on the old RBO board that you posted a seawater pump impeller part number for a poly/ neoprene type impeller that would wear better than the standard rubber Merc impellers - am I remembering correctly and if so, could you post the alternate part number again? I replace my impellers every 3rd season and will be doing this task over the winter among other things. Thanks!

Dream_Inn

That's good news Tiki.  I'll have to look at my spare impellers to make sure they don't fit the recall.  Keep us updated!

TonyWalker

Here is a thing that happened to us while we were on the loop in 2010.  The starboard engine temp gage started a slow but steady climb from normal to higher and higher temps.  Eventually I shut that engine down because the alarm signal was inevitable.  This was on the southbound on the Mississippi River on our way to the "Little Diversion Canal."

Long story short, we were anchored in a group so I had lots of help.  The problem turned out to be the impeller.  You could turn it by hand and the blades would follow.  But if you started the engine, the sudden torque would turn the hub but the blades which had separated from the hub just sat still.  Thank you to Don and Rosie, aboard the M/V "Just Rosie" for staying with us and the folks at Marsh Harbor Marina here in FL by phone for helping us to get going by 10:00 am in the morning.

Always carry spare impellers.

Tony

Salt Shaker 342

frodo13056

Hey Al, thanks for the update on the neoprene impellers and the recall issues with the standard Merc impellers. And a huge thanks to Tiki for starting this threading saving many of us that may be changing impellers from potential overheating issues in the spring! This thread actually makes me kind of wonder about a guy on my dock that overheated his engine on his first trip out this last summer. According to him, he got about a mile out into Lake Michigan and he overheated his Merc. 8.1 liter engine and he had his impeller replaced just prior to launching in the spring. That overheating warped the head and cost him about $4k and lost 3 weeks of use....... I figured that the marina that did the work probably messed something up but this thread points to possibly an issue with the new impeller. This is one of the main reasons for frequenting this site - great bunch of folks always willing to go out of their way to help others out!

Black_Diamond

Another 'lucky we have Al' moment or I bet none of us would have known about this!

TikiHut2

Man, who'd have thought that there'd be such weird complications to such a simple and often changed part. Hubs that spin out and even recalled OEM mfg problems for tolerances that you just wouldn't notice. Hope this thread saves somebody else a huge headache, especially those with hard/impossible to reach pumps.

The forum really works best when everyone shares their experiences (even if you think it's insignificant). There has been some great input that's brought insight to all of us DIY'ers who love these boats and enjoy fixing problems or just spending time tweaking systems.

Kudos to Al and thanks again to EVERYONE with that common Rinker bond who make this site so helpful.....and a nice break from the daily grind.
Cheers, Mike

SeaShift

This post is upsetting me slightly. I just replaced both water pumps because I was unable to get a prime. Every time I put the boat on the lift it would not pump water the next time out. I had to continuously climb in the bilge and open the drain on the incoming line then I would be fine. Wonder if I can get my money back on the two new pumps??

TikiHut2

SS, I assume you mean you were purging air from the line by "opening the drain on the incoming line". I've never had to prime a seawater pump and we trailer every time we use the boat like /thousands/millions of other mercruiser owners. I guess I'm not sure what you meant in your post.

Obviously any water pump will burn an impellor in seconds if it's run dry. Is someone closing the seacock on your water intake when the boats pulled? I guess I need a bit more detail.
Mike

Dream_Inn

I guess I'm wondering how you did not have water at your pump before you started your engine?

I keep my boat on a lift and have had boats on a lift for 8 years now (as well as 100s of others in my marina) & never had an issue. 

Now, issues with getting prime on air conditioning is another thing, I always close my seacock before I lift (didn't have to with last boat).