Impeller spun?!?!?!?

[fritzL]

So the bote overheats...
I take her on shore and get the time to do.an exploratory and find this.
See image.
The impeller blades have ground down and burnt...the impeller housing, metal part...is now round and has shifted. the small rubber inlet tube is clear... check via blowing.through it.
I will.check the thermostat next, as soon as i receive the new hoses and thermostat...
By the way, is there any reason i could not use an automotive thermostat?




What could cause this?

 

[nnl1987]

Not having the outboard/outdrive low enough in the water when starting the engine will do it. Also age of it.

What are you running a stinger or cobra? My guess would be a cobra as it's the same impeller/housing as mine. They sit a lot higher in the water versus a mercruiser i/o or a outboard motor which sit in the lower gear case.

You should run a marine t stat as marine engines run at different temperature then a automotive engine. They are not expensive just a matter of getting your hands on one.

 

[fritzL]

It is a cobra.
How long should the intake hose, looks like 1/4" ID be... could it be too short for water intake?

 

[nnl1987]

Water is pulled up from the lower gear case, were the screens are just under the cavitation plate is. My screens were kind of falling a part, there's a chance yours might be gone completely if you are trying to look for a reference.

The 1/4 tube is for either drainage or possibly a vent hose.

 

[fritzL]

Would the qater be fed from
PART #: 0911706 TUBE, Water supply
As seen in the parts schematic

 

[Scott Danforth]

impellers need to be submerged when starting or fed by muffs. 20 seconds without a good water supply and they are toast

older than 5 years and they are toast

try to suck water from a bucket and they are toast.

marine thermostats are stainless. so use the correct one.

additionally, without the impeller, there is no water flow to the motor. the motor overheats and your exhaust goes from 200 F (mix of water and exhaust) to 1100F (pure flame and exhaust) so your flappers are gone, the rubber exhaust hoses are probably burnt as well.

 

[fritzL]

Thanks...
I must have been getting some water.
The rubber exhaut hoses are intact. I have a new replacement impeller, housing, plates, oring and gaskets.
The feed hoses are old and have new ones on the way.
How can i verify that water is being pumped by the impeller? Besides clear hoses...
Thank you all for reading and help

 

[Scott Danforth]

Pull line from the drive with motor running either on muffs/hose or in the lake and aim it up. Water will be flowing out about 6-8" at an idle. Then reinstall and go boating

 

[fritzL]

By line from the drive, you mean the raw water feed to the thermostat inlet...yes?

 

[Scott Danforth]

Yes

 

[fritzL]

Thanks.
Here is the question...
I have removed the impeller.cover to replace it.. so i thought i would start the water and see if the muff would supply the impeller chamber. They did not.
There was leakage. If i compressed by hand the muff together the leakage ceased and water did flow out of the chamber.
Will a properly sealed impeller have enough suction to prime itself and feed the water pump?

I also removed the thermostat and it is rusted almost shut. Not smooth action at all. New marine one ordered along with replacemwnt hoses.

 

[nnl1987]

I had the same experience with my omc, squeezing the muffs by hand. After discovering that I have always trailed it to a river or lake to test it. Pretty fortunate that it's only 5 minutes away. I don't trust muffs anymore.

If you trim down at the boat launch before starting the engine in the water there will be a point where the impeller will be fully submerged and priming won't be an issue.

As long as it is sealed properly and there is no blockage in the line between the transom mount and the water pump, the impeller will feed the water pump.

You could take the heater hose off the water pump and take a garden hose and push water backwards to flush anything out with the impeller off.

 

[fritzL]

nl1987,
thanks for the reply, and stating that, if the impeller chamber is properly sealed, there will be enough vacuum to pull up water to prime the impeller.


I am planning to vacuum out what I can from the manifold, item 36, and was going to ask about running water through the "heater" line, item 25, as you pointed out. the other line item 23, I would disconnect at the bitter end from the thermostat housing, and run water through.

Item 35, exhaust flapper, melted away, I am not sure where the debris for this is. would the debris have exited the system?

 

[nnl1987]

Not sure about a 4 banger like yours but if you look at your exhaust bellows theres a chance it comes slitted with holes (factory design) for what I assume is drainage. Have to trim all the way up. You might be able to see pieces of the exhaust flapper or they might have already be gone.

Fairly good chance they are still in there. The best thing to do is pull the outdrive, have a look. Can also use a bore camera and put it in exhaust bellows. Cameras are fairly cheap on Amazon.

If you do choose to take it off good time to grease u joints, shaft assembly as well as inspect your bellows, exhaust bellows, grease your shifting lever and roller. The gasket between the transom assembly and outdrive is cheap.

 

[fritzL]

Hello All,
Have replaced all the hoses, thermostat, and impeller. While the hoses were off on one end, i ran a garden hode through them, effectually back flushing...

Still runs over 175*F as per dash mounted gauge.
When the belt was off i could move the water pump rotor by hand and it felt smooth... no obstructions or grinding.

I could feel the cold water feom the muffs on the fresh water draw side...
And the warmed water on the output side hose.
Does anyone have an idea why this bote appears to be running hot?

3 years and counting now that i have been debugging this free bote.

I am near Lake Geneva Wisconsin ...
I have cookies.and beer...

 

[flashback]

The impeller cannot prime itself, it must have water forced to it with muffs. Alternatively the drive must be submerged in the lake deep enough that the impeller is below the surface..

 

[fritzL]

The impeller cannot prime itself, it must have water forced to it with muffs. Alternatively the drive must be submerged in the lake deep enough that the impeller is below the surface..

I have a tight fitting set of muffs. Before I ut the impeller cover back in place, I verified that water from the garden hose/muffs was POURING out of the impeller chamber. In one f my previous posts I stated that I saw almost no water coming out this was due to poorly fitting muffs. I had use dht elong rectangular ones and it was a leak fest. I bought smaller round ones and they fit better.
I did take the bote out on the lake, the depth allowed me to lower the outdrive to the maximum, then with drive submerged , I started the engine. In a matter of a few minutes the temperature gauge was over 175*F.
The lake temperature was about 73*F.

 

[flashback]

Have you checked the accuracy of your temp gauge?

 

[fritzL]

I could, given an approved method. I have a laser thermometer. I was thinking of aiming it at the centermost point of the block and comparing to reading of the dash mounted thermometer... If you have another idea, please share
F

 

[flashback]

Thermostat housing is where the boat gauge gets it's temp so that's a good place to start but while you're at it you might as well check other areas...and yea the if thermometer would be fine...