IMPELLER WON'T PRIME

[eyepeeler]

On my friend's 2004 RLXI when he first starts the boat and idles, the impeller doesn't prime. When he increases the rpm, the impeller primes and stays primed the rest of the day. The impeller is new, he checked the gasket, the intake hose and the hose clamps. Has this happened to anyone else? Any ideas?

[skier92]

Was the new impeller rotated in its proper operational direction when it was installed? Flexing the blades the incorrect direction would likely cause inefficient operation. Also, does he have a heater with a "Y" fitting installer before the raw water pump. I've wondered if this would cause the same problem your friend is having. That's the only reason I could come up with as to why Malibu mounts them after the pump.

[eyepeeler]

He has a heater but I don't think he has the"Y" fitting.

[skyskier]

Were there any chunks missing from the old impeller? If so, you need to start looking downhill of the impeller to see where the chunks landed.

[VinRLX]

Is the raw water valve completely open on the through-hull fitting?

Does he have the correct new impeller and is it installed facing the correct direction?

Anything before impeller that might cause air leak--flush pro, raw water strainer?

[Bake's Marine]

Thru-Hull check ball valve shut off? Make sure it is in-line with the hose.

On the indmar Johnson impellers you can put it in with the splines facing the wrong direction and they will correct themselves. On a Mercruiser Engine Impeller, that's a different story, they have to be going the correct direction.

-Paul

[eyepeeler]

He has a shut off valve. It appears to be open. Do they ever get clogged or partially clogged?

[RTS]

He has a shut off valve. It appears to be open. Do they ever get clogged or partially clogged?

The valve, and the pickup grate below the boat, can and will get clogged with debris. Try discconnecting the raw water inlet hose from the impeller housing and put a high pressure garden hose in it to flush anything out.

[eyepeeler]

Thank you everybody. I will advise my friend of your comments and suggest back-flushing that shut off valve.

[the_dude]

Thank you everybody. I will advise my friend of your comments and suggest back-flushing that shut off valve.

Please post back if you are able to determine a problem and fix it.

I had this exact symptom on my 97 VLX and in 60+ hours of use and an impeller change it always did it. Each time I first dropped the boat in the water I had to blip the throttle a bit and then was fine the rest of the day.

I never figured out the problem.

[Green_Giant]

So I had this problem today. Changed the impeller in the driveway last week, kind of forgot about this issue and as we idled away from the launch I see the temp climbing quick, it just gets to 205 and beeps as I shut it down, steam coming off the exhaust out back but not a ton. Impeller housing was HOT. I let it cool off a bit, restarted and gave it a quick goose and it shot right back down to 160 and the housing was immediately cool to the touch, (finally primed.)

I didn't feel good about running with that impeller so I shut the through-hole valve and pulled it out and though new, all the blades had assumed the perma-bent-over position, no missing fragments. That thing must have been torched in there, my old one looked much better after an entire season of use.

I popped the old one back in and we were off to the races. I believe everything is ok based on it being literally seconds up over 200 degrees, and it ran like a top for the rest of our session, no smoke / steam or temp issues.

Anything else I should check / worry about?

(as for the previous poster, I think this is caused when all the water has drained out due to a impeller change or other winterization activities and the low RPM's aren't quite enough to suck the water up and prime the pump. Only solution I can think of would be to remember to give a quick goose upon the next startup and monitor the impeller housing for the first bit if you can remember better than me )

Edited May 27, 2009 by Green_Giant

[BuFootin]

I have been battleing the same exact problem in my 05 RLXi this year. My scenario is I have the Y fitting for the heater before the impeller pump. When I start the engine at idle the impeller pump will not prime. If it remains at idle the impeller housing and engine temp will get hot. As soon as I rev the engine the pump primes and water flows without problems the rest of the day. This as happened each time this year. I don't believe it is related to having the block/engine drained from winterizing.

I too would love to hear what other find. In the mean time, I make sure and rev the engine right after it starts. But I don't like this as a "work around" because I know the pump should prime at idle and flow water.

[BuFootin]

So I had this problem today. Changed the impeller in the driveway last week, kind of forgot about this issue and as we idled away from the launch I see the temp climbing quick, it just gets to 205 and beeps as I shut it down, steam coming off the exhaust out back but not a ton. Impeller housing was HOT. I let it cool off a bit, restarted and gave it a quick goose and it shot right back down to 160 and the housing was immediately cool to the touch, (finally primed.)

I didn't feel good about running with that impeller so I shut the through-hole valve and pulled it out and though new, all the blades had assumed the perma-bent-over position, no missing fragments. That thing must have been torched in there, my old one looked much better after an entire season of use.

I popped the old one back in and we were off to the races. I believe everything is ok based on it being literally seconds up over 200 degrees, and it ran like a top for the rest of our session, no smoke / steam or temp issues.

Anything else I should check / worry about?

(as for the previous poster, I think this is caused when all the water has drained out due to a impeller change or other winterization activities and the low RPM's aren't quite enough to suck the water up and prime the pump. Only solution I can think of would be to remember to give a quick goose upon the next startup and monitor the impeller housing for the first bit if you can remember better than me )

Interesting that this happened to you after you changed your impeller. I too installed a new impeller & gasket this spring. Where did you purchase your impeller? BTW if you leave the impeller out of the housing the blades will straighten out. If they don't then for sure the impeller is trashed.

[Green_Giant]

Interesting that this happened to you after you changed your impeller. I too installed a new impeller & gasket this spring. Where did you purchase your impeller? BTW if you leave the impeller out of the housing the blades will straighten out. If they don't then for sure the impeller is trashed.

Interesting, I was kindof hoping it might straighten out so left it in my boat kit for now, at least as a suitable backup. It came from SkiDim.

I too have added the Y adapter last fall but used it a ton of times since then, but have only had the priming issue twice and both after an impeller inspection / replacement, once in the driveway on fake-a-lake and this morning so I actually don't think it was a water pressure issue and I have no leaks, all connections are tight.

That Y adapter theory is an interesting one however, introducing another path in the intake line that could get air in especially after pulling the impeller, since the other end of that Y pipe (via the heater) is where the heater gets its hot water from at the top of the block / intake manifold I think.

[BuFootin]

Interesting that this happened to you after you changed your impeller. I too installed a new impeller & gasket this spring. Where did you purchase your impeller? BTW if you leave the impeller out of the housing the blades will straighten out. If they don't then for sure the impeller is trashed.

Interesting, I was kindof hoping it might straighten out so left it in my boat kit for now, at least as a suitable backup. It came from SkiDim.

I too have added the Y adapter last fall but used it a ton of times since then, but have only had the priming issue twice and both after an impeller inspection / replacement, once in the driveway on fake-a-lake and this morning so I actually don't think it was a water pressure issue and I have no leaks, all connections are tight.

That Y adapter theory is an interesting one however, introducing another path in the intake line that could get air in especially after pulling the impeller, since the other end of that Y pipe (via the heater) is where the heater gets its hot water from at the top of the block / intake manifold I think.

My impeller came from SkiDim too. I have had others on here warn about the Y adapter causing priming problems, but there are many folks that also don't experience priming problems with the Y before the raw water pump. I wonder if there is a bad batch of impellers out there? Have you experineced any priming problems with your old impeller installed?

[Green_Giant]

My impeller came from SkiDim too. I have had others on here warn about the Y adapter causing priming problems, but there are many folks that also don't experience priming problems with the Y before the raw water pump. I wonder if there is a bad batch of impellers out there? Have you experineced any priming problems with your old impeller installed?

I suppose could be bad but I've always got my impellers from them w/o issue, they're great.

I'm not sure you'd always know that your impeller isn't initially priming since most of the time a little gas is given to go anywhere or just out of habbit upon startup.

If it is the Y adapter, it might be interesting to explore pulling the hot water off another location lower on the block? (less chance for air pockets?) but not sure if there is such a spot. Knock sensor and shower occupy the two I'm aware of.

[BuFootin]

My impeller came from SkiDim too. I have had others on here warn about the Y adapter causing priming problems, but there are many folks that also don't experience priming problems with the Y before the raw water pump. I wonder if there is a bad batch of impellers out there? Have you experineced any priming problems with your old impeller installed?

I suppose could be bad but I've always got my impellers from them w/o issue, they're great.

I'm not sure you'd always know that your impeller isn't initially priming since most of the time a little gas is given to go anywhere or just out of habbit upon startup.

If it is the Y adapter, it might be interesting to explore pulling the hot water off another location lower on the block? (less chance for air pockets?) but not sure if there is such a spot. Knock sensor and shower occupy the two I'm aware of.

Totally agree. SkiDim is awesome. Use them all the time too. Grasping at staws maybe, but was thinking their supplier/manufacture may have produced a bad batch. In my case, I have used the fake-a-lake for the last 12 years in the driveway. This is the first time I have ever had a problem with the pump priming and drawing water from the fake-a-lake (or the real lake). Always witnessed water being drawn in at idle, because I was always afraid of the fake-a-lake falling over and the engine overheating.

I may plug off my Y connector and heate hose next outing and see if it primes at idle. That will for sure isolate the Y connector. If it still does not prime....then I'm lost.

[scfdfireman]

I’m sorry, but it seems that my previous post didn’t show up as I intended… Anyway, here’s the info…

The way the raw water impeller works is to create a vacuum in the tubing, valves and transmission cooler (on V-drives) in order to draw in the water from the water inlet on the bottom of the Bu and then pump the water and prime the centrifugal water pump on the front of the motor. In order for it to be able to draw in the water, the amount of vacuum it's able to create is critical as it effects how long it will take to draw in the water (which also cools and lubricates the pump impeller). The amount of vacuum that’s created is affected by any loose clamps, fittings, impeller condition, pump housing condition, collapsed intake hose and rear seal condition. One simple method to check for leaks is (as mentioned above) to disconnect the raw water intake and attach a garden hose. Turn the hose on with the motor off and check for any leaks (look for small drips). Next, start the motor and check for leaks (drips) at the back of the raw water pump and the pump cover. Once all the leaks have been eliminated and if the problems persist look for issues with the pump itself. Any score marks or scratches to the inside of the housing (including the front plate and back housing) from overheating or from sucking up debris will greatly effect its performance. One small but important feature to the raw water impeller are two small groves on each side of the impeller hub just above the brass center. These small groves allow a small amount of water to flow into the front and back of the housing to seal and cool these areas of the impeller, housing and rear seal. They’ll be easy to see on a new impeller, but a used impeller may have them filled with debris, grease or worn to a point where their no longer there and could have caused damage to the housing. If you still have problems, trace down the hose from the raw water pump to the intake. Since its cold water only there shouldn’t be any other rubber lines running off of it, but you never know… One last thing (shown below) is what Johnson Impellers suggests on impeller issues.

Reduced flow will occur when the impeller is damaged. However, bowed, missing, work or ripped blades will cause reduced flow. A worn cam, wear plate, or cover plate will also reduce flow. The replacement of these parts when worn actually cures the problem. Another cause of low flow is an air leak. This can occur anywhere along the suction line, within the sea strainer, or within the pump. Check all hoses, pump gaskets, hose clamps, fillings and the pump water seal. Regularly clean your suction strainer and confirm all old impeller blades are removed when replacing your impeller.

How to prevent pump failure: The main causes of premature impeller failure involve running the pump dry, with a restricted suction or with a blocked discharge. Confirm your inlet seacock is in the open position before engine start. You would be surprised how often this simple step is forgotten. Regularly clean your suction strainer and confirm all old blades are removed when replacing your impeller. These steps will reduce the majority of system flow restrictions.

Edited May 28, 2009 by scfdfireman

[the_dude]

I've decided that my prime issue is caused by disconnecting the raw water hose between the v-drive and raw water pump each time I pull the boat in order to flush the motor. Before I can get the hose back on a lot of the water drains out and creates a big air pocket.

[scfdfireman]

If "a lot of water drains out" then you have an air leak up-line... It's similar to using a straw and covering the tip with your tongue as fluid is drawn up. With no air the fluid holds in the straw (or container, or raw water line). However, as soon as air is introduced all the water runs out of the straw (or raw water line). With vacuum a small leak creates big issues...

Edited May 29, 2009 by scfdfireman

[rustie]

One of the Globe "run dry"impellers might help too. I just ordered a couple of the #100J to replace my standard rubber impeller. With this new impeller, I will be able to fire the engine right after trailering to blast all water out of the exhaust system (and the engine itself)....which always removes a LOT of unwanted moisture from the entire system during storage. No reason to leave it in there to corrode all the aluminum components....especially the alum heads in a HH 383!!!

[ed obermeier]

One of the Globe "run dry"impellers might help too. I just ordered a couple of the #100J to replace my standard rubber impeller. With this new impeller, I will be able to fire the engine right after trailering to blast all water out of the exhaust system (and the engine itself)....which always removes a LOT of unwanted moisture from the entire system during storage. No reason to leave it in there to corrode all the aluminum components....especially the alum heads in a HH 383!!!

Just asking for the sake of information - is it really a good idea to do that, even with a run dry impeller? I thought the idea with a run-dry was IF something happened where you had occasion to accidentally run it dry for a few seconds it wouldn't trash it to the point of failure. I'd think a few times running any impeller dry for even a few seconds would kill its functional service life but I don't have any experience with running a run-dry dry. Opinions?

Ed

[skier92]

I wouldn't. It's a water pump, not an air pump!

[scfdfireman]

Actually, the raw water impeller is an air pump, that's how it's able to draw a vacuum and pull in the lake water. A correctly operating raw water pump will have a slight vacuum on the inlet side of the pump and a pressure on the discharge side of the pump. However, this depends on all the connections, seals and other factors being like they're supposed to be.

[rustie]

Actually, the raw water impeller is an air pump, that's how it's able to draw a vacuum and pull in the lake water.

Yep...fireman is absolutely correct...it is an air pump, and vacuum to be exact (as he said). When you first launch your boat, there is no water in the pickup lines. Water must be drawn up into the pump by suction before any "pumping" action can occur. I haven't actually measured the distance in my LSV, but an educated guess is that water must be initially drawn up at least through 2 feet of hose, and maybe as many as 4 feet (depending on how it's routed in each hull). That means any rubber impeller is running dry for at least a few seconds before being primed....

As for the synthetic blue Globe impeller, they state it is GUARANTEED to run DRY for 15 minutes. Now that will create a LOT of heat....and the impeller still survives. So, a 5 or 10 second blast while trailered at the end of the day would not likely do any harm whatsoever....and it would remove a heck of a lot of water from several systems (the best for long term seasonal storage if yew axes me).

Check it out here:

http://www.globecomposite.com/pages/products_impeller