Shredded Impeller

[scumfrogmillionaire]

So anybody have a clue why this would have happened? Replaced the impeller this spring. Ran the motor all over the place for a week straight. Let it sit for a month. Go to fire it up with a barrel of water (difficult time starting). Had to rev the engine to get it started, then idled fine after awhile but realized no water coming out from telltale. Dropped the lower unit and the impeller is completely toast. Why would this be? I never ran it out of the water. Literally first time firing it up in like a month and this happened. I will replace the impeller but am worried it'll happen again?

 

[racerone]

Was the water level in your barrel 6" above the pump , yes or no ?

 

[scumfrogmillionaire]

no Water was just above the inlet strainers. Have never had an issue before with the same level..

 

[Bt Doctur]

water level MUST be above the cavitation plate for the pump to MOVE the water
Run it on earmuffs and you`ll be just fine

 

[scumfrogmillionaire]

So just running it with the water level an inch above the inlet screens destroys the impeller?

 

[racerone]

Yes it does !!----These pumps do not prime themselves !!

 

[MTboatguy]

Needs Mo Water!

 

[scumfrogmillionaire]

I figured it was something stupid like that. I'm an idiot. Thanks guys. I will fill the water as high as possible to prime the pump once i replace the impeller (or just use muffs). Do you guys normally use grease or petroleum jelly on your impeller when you install it?

 

[Dukedog]

ok.. someone needs ta explain to me why water needs "way" above inlets ta make water circulate?.. tha only place water inters tha system is through tha inlets.. no where else... don't understand "prime"?. how to?.

tha only way I can find a way ta buy into it is if tha water is jus barely above before ya start it and after starting, putting in gear tha "disturbed water" falls below tha inlets?

 

[racerone]

Water needs to be 6" above the pump in a test bucket !!

 

[Scott Danforth]

I figured it was something stupid like that. I'm an idiot. Thanks guys. I will fill the water as high as possible to prime the pump once i replace the impeller (or just use muffs). Do you guys normally use grease or petroleum jelly on your impeller when you install it?

KY jelly, never ever use a petroleum product

 

[Scott Danforth]

ok.. someone needs ta explain to me why water needs "way" above inlets ta make water circulate?.. tha only place water inters tha system is through tha inlets.. no where else... don't understand "prime"?. how to?.

tha only way I can find a way ta buy into it is if tha water is jus barely above before ya start it and after starting, putting in gear tha "disturbed water" falls below tha inlets?

impellers only push water, they do not pull water.

so when the boat is sitting idle in the water, the water is about 10" above the inlets, and it primes the pump, you start out, and the force of the water from the boat moving keeps the water flowing to the pump.

or use muffs to have the hose push water to the pump.

not having the water high enough when you first start it only takes about 20 seconds for the impeller to go into melt down as it needs the water to lubricate it and keep it cool.

 

[GA_Boater]

ok.. someone needs ta explain to me why water needs "way" above inlets ta make water circulate?.. tha only place water inters tha system is through tha inlets.. no where else... don't understand "prime"?. how to?.

tha only way I can find a way ta buy into it is if tha water is jus barely above before ya start it and after starting, putting in gear tha "disturbed water" falls below tha inlets?

The intake is below the pump and if the water is only at the intake level, the pump is high and dry, only beating air.

Prime means to fill the pump with water so the water has to be above the pump. Next time you change an impeller, look at the pump with the water ports on the bottom.

 

[Dukedog]

The intake is below the pump and if the water is only at the intake level, the pump is high and dry, only beating air.

Prime means to fill the pump with water so the water has to be above the pump. Next time you change an impeller, look at the pump with the water ports on the bottom.

answer I was lookin' for... know tha coollin" system but have never used a "bucket".. only hose or lake so pump to intake location never was an issue to be thought out!

 

[scumfrogmillionaire]

Thanks for the explanation. It all makes complete sense. Not sure how i didn't notice this.

 

[MTboatguy]

answer I was lookin' for... know tha coollin" system but have never used a "bucket".. only hose or lake so pump to intake location never was an issue to be thought out!

"pump" in an outboard is really kind of a misnomer, because it does not pump anything there is no suction created when the impellers are spinning, they are simply pushing water and not pumping water.

 

[racerone]

???----Yes there is suction created by the changing volume between the vanes at low speeds and it is a positive displacement pump.----At high speed it becomes a centrifical pump.

 

[MTboatguy]

However you want to think about it, you didn't have the motor deep enough to prime it which caused the meltdown of the impeller,

 

[Chris1956]

Also, check the water inlet holes. On my MerCruiser, left in salt water, the barnacles liked to live there and they would impede waterflow. I had to remove the wearplate and crop 'em out with a screwdriver, from above.