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impeller question


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Well, I thought I had the magical impeller that would never need changing. Although I read about inspecting and replacing and what not on here and MBO, I always thought I took just a little bit better care of my stuff than the rest of you bandwith wastrels and figured I was immune.

7 scouts, 3 leaders, gear, pffftttt........

Swapped out the bad boy from one of TWO I carry on board (although I did have the almighty impeller it never hurts to be prepared) in about 5 minutes and we were back in business for the rest of the day.

Until... heading back to the ramp with all 10 aboard at high rpm for about 15 minutes, she started to sound like a helicopter's blade thump from under the engine cover. I throttled back immediately, looked at the temp and she was fine. I puzzled for a moment at the engine cover, sure that my fervent stare would fix whatever was wrong underneath. One of the boys said "uh, there's smoke coming out of the side over here, is that right?" All scouts ordered into the water, I grabbed the fire extinguisher, pulled the pin and readied myself to open the cover. (not wanting to give whatever was under their air for fuel....nice teaching moment)

Lifted the cover, and found boiling water up to the carpet in the bilge and condensation all over everything. What he had seen was steam. The hose on the outbound side of the impeller had come off and the obviously the impeller had been pumping water into the bilge...but why boiling? and why not indication on the temp gauge? Could it be that the engine was so hot that it heated the bilge water up so much purely by proximity? (if so, I'm screwed)

Anyway, I hooked up the hose , she started right up, sounded right and we idled into the ramp area from where we were, about 200 yards.

All the way home I postulate as to why the hose came off....I figure that the bits of chewed up impeller made their way down the line to a screen of some sort, and plugged it up. The new impeller was doing it's job magnificently, pumping all sorts of cool water at high RPM down a hose that had a blockage at the end. Pressure built to the point of blowing off the hose.

At home I pulled the hose off again immediately after the impeller. I'm sorry that I don't know what it attached to at the other end, but a can a little larger than a coke can. I poked a finger up into the can and felt a screen, with bits of rubber all over in it. I got those out, but they don't add up to 1/3 of the missing bits from the first impeller. I took of the hose on the other end of the sealed can like thingy and felt another screen, but in this case I would be feeling the wrong side of the screen for debris.

Is there somewhere else I should look? or did they wear small enough to pass through the screen and out the back of the engine?

Any thoughts? DD Monsoon

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Sounds like you did the "Safety First Boy Scout thing" by getting the kids out of the boat. Smart thinking.

I would think what did not get caught in the screen would have passed through your system and out. You could pull the plugs and drain your block just like you would for winterization and flush a lot of water through just in case.

I had a similar thing happen a few years ago on an I/O I had. The engine got so hot that it melted the hydraulic lines to the lower unit. The hydraulic fluid started smoking and I thought I had a fire. Lucky it was just smoke.

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Yeah, you should be just fine.

What you're referring to is the trans cooler and when it get's badly clogged it will usually cause one of three things to occur:

1. overheat engine

2. hose to come off

3. hose to burst

As you learned, it only takes a couple of minutes to check it and clear out any debris. In addition to impleller pieces, weeds getting stuck in their can cause the same problems.

Mike

Edited by mlange
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As you learned, it only takes a couple of minutes to check it and clear out any debris.  In addition to impleller pieces, weeds getting stuck in their can cause the same problems.

Mike

How often do you check for any debris?

Last year when I had the dealer do some other work they also changed the impeller. They made a comment that there was a lot of debris in the impeller screen - weeds, small sticks and such. The water in go in does have a lot of debris early in the season and late in the season. I have an extra impeller I carry, but have never personally changed or checked it.

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I think this all depends on where you boat. I never get anything in there on a regular basis, so I just clean it out when I change my impeller every spring.

If you are somewhere where you can get lots of crap sucked up, then I'd probably just check it every month or so.

More importantly, though, you can usually tell that you've got an issue if your temp gauge gets up above 165 from time to time. Lots of times when you have a clogged up filter it will be ok at speed, but when idling it may creep up a bit.

This, of course, assumes a temp gauge that is accurate.

Mike

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Thanks, I feel better now. :)

This morning while still mulling over the situation I thought maybe the reason the water was so hot was that it had been in contact with the mufflers near the back, which cause the steam shot that the scout saw near him on the back seat. I just couldn't figure out why the water was so hot if it was lake water filling the bilge due to the popped off hose. This must have been what happened to make the water so hot and the steam.

case closed, thanks again.

Edited by jayjoans
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If water was splashing around because the bilge was full, it probably splashed on the exhaust manifold at the head. It is still quite hot there. Hot enough to make steam. Plus the fact that the engine was probably getting hotter than normal.

Also, if the there was no water circulating in the engine and the gauge indicated no over heat, I would keep an eye on everything for a while. If the sensor does not have water on it, it does not register the correct temp of the engine until it is to late, as mine did.

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At home I pulled the hose off again immediately after the impeller.  I'm sorry that I don't know what it attached to at the other end, but a can a little larger than a coke can.  I poked a finger up into the can and felt a screen, with bits of rubber all over in it.  I got those out, but they don't add up to 1/3 of the missing bits from the first impeller.

Jay,

When the hose popped off, all water higher than that point comes back out the other way, due to gravity. This has a tendency to backflush the tranny cooler and flush out bits of the impeller with it.

The water coming back out will also be very warm (shouldn't be boiling hot, but I'm not sure how long you were running without the cooling.)

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This has a tendency to backflush the tranny cooler and flush out bits of the impeller with it.

The water coming back out will also be very warm (shouldn't be boiling hot, but I'm not sure how long you were running without the cooling.)

Wow, this makes perfect sense, now even the bits are most likely accounted for.

Thanks!

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Stories like this make me want to pull off the hose, check for debris, and change the impeller just to be safe. Then I remember that I have a V-Drive and the impeller is wedged in between the engine and the transom. Anybody have any tips for making the change?

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On the vDrive it just takes a little more time. To ease the pulling process once you have the cover off squirt a little dish soap in and crank the engine (with out the safety lanyard) and the impeller will slide out when grabbed with pliers. Soap the new one and you job should finish up in no time at all.

If you do not lubricate your impeller the pulling process will involve bandaids for your knuckles.

Have fun!

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On the vDrive it just takes a little more time.  To ease the pulling process once you have the cover off squirt a little dish soap in and crank the engine (with out the safety lanyard) and the impeller will slide out when grabbed with pliers.  Soap the new one and you job should finish up in no time at all.

If you do not lubricate your impeller the pulling process will involve bandaids for your knuckles.

Have fun!

thanks for the tips.

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Off Topic:

JayJoans - I'm registered down in Santa Clara County with BSA. I used to be the finance chairman for the Gavilan District. How active are you with that troop? Have you done Woodbadge? Just had a friend that came back from Philmont, said it was incredible.

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Off Topic:

JayJoans -  I'm registered down in Santa Clara County with BSA.  I used to be the finance chairman for  the Gavilan District.  How active are you with that troop?  Have you done Woodbadge?  Just had a friend that came back from Philmont, said it was incredible.

Staying off topic.

I was very active with the troop my boys were in before they aged out. They both made it to Eagle.

I went through Woodbadge and went to the Natl Jambo on the medical staff 4 years ago. I was supposed to lead a group at Philmont, but that fell through and they went the next year (and this year) when I couldn't go. The stories and the pictures from the Philmont experience are incredible.

One thing we never got organized was to head up a Waterskiing and Motorboating merit badge class. A number of us in the troop talked about it, but it just never happened. I organized Snow Sports (skiing and snowboarding), Rocketry, in addition to many First Aid, Family Life, etc classes. I regret never getting the Waterskiing one going. I may still offer it to the troop. I wonder if they have added wakeboarding yet. They changed the snow skiing one to add snowboarding to it.

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Shouldn't you pull the intake hose and ck it as well, not to mention the intake grate. I picked pieces out of it when I blew my first impellar. just FYI ,mike

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