Impeller prediction... will it work?

MrLundt

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For anyone who viewed the "What do I have?" thread, you know I have a 1977 Ford/OMC 302 w/ 190 H.P. V8 and an electric shift stringer outdrive on a 20' Larson Manta. After resolving some ignition issues, I think it's ready for a test run at the lake. It runs well in the driveway but I didn't want to run it more than a minute or two w/o a water source. What are the chances that, after 6 years of storage in my Dad's barn, the impeller will work. Is there any way to check this before going to the lake?

I've replaced the plugs and the ignition coil. I've checked the lubricant in the upper and lower unit of the outdrive and I've drained out the old fuel from the gas tank. Is there anything else I need to do before this test run? Thanks in advance for your words of wisdom.
 

Don S

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Re: Impeller prediction... will it work?

It runs well in the driveway but I didn't want to run it more than a minute or two w/o a water source

Does this mean you have been running it for a minute or two WITHOUT water????
 

Bt Doctur

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Re: Impeller prediction... will it work?

If you ran it without water, then NO
10-20 seconds ,dry from storage, and no water ,you more than likely trashed the impeller.
 

MrLundt

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Re: Impeller prediction... will it work?

:( Yes, I ran the engine for about a minute w/o water. My intention was to see if it would start after some of the ignition tinkering I had to do. After it started I engaged the propeller for about 5 seconds to see if it would shift into gear. Which does the damage... the prop or the engine or both? Do these new details change your prediction? Is there any way to check the impeller before I haul it to the lake?
 

Don S

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Re: Impeller prediction... will it work?

The pump turns with the engine. IF it didn't, you would overheat when in neutral.
Running a dry impeller for a minute is a killer. You need to replace it BEFORE you head for the water, or you WILL overheat.
 

chiefalen

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Re: Impeller prediction... will it work?

You have a manual? You have to split the lower and upper drive.

Water pump will be in the bottom of the upper.

Sir with this drive you never ever run it with the drive up only fully down.

And with any boat never run it without water going to it.

As little as 30 seconds will trash your impeller.

Ok with water going to the drive fully down start it. There is a telltale stream that will shoot water on the ball gears.

To see it look behind drive fully down you see the ball gears? When running should see water shooting on the gear.

No telltale stream shut it down fast 15 seconds max.

Thats how you tell if your water pump is working.

My prediction: Jets win the super bowl this year.
 

MrLundt

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Re: Impeller prediction... will it work?

I hope you still believe that there's no such thing as a stupid question after I ask this. With my outboard, I use a hose w/ muffs when I want to run it at home. The water intake on the OMC is obviously different. There is a hose attachment on the high side of the upper drive unit. Is that for the water source when running the motor in my driveway. My manual (yes, I have a manual) illustrates this for "flushing the system" when I winterize. I would think that if there was a hose w/ water pressure attached there, I would see the "telltale stream" shooting on the ball gears and attribute it to the hose pressure and still not be sure if my impeller was working. Am I just not supposed to start this at all out of a lake or body of water? Is the hose fitting an acceptable way to cool the engine while running in the driveway? Is there some other way to provide water to this thing besides putting it in a lake? OK, I'm ready now. Let the scolding begin.
 

chiefalen

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Re: Impeller prediction... will it work?

No scolding. You can hook up muffs to the water intake just like any drive outbard-inboard.

And no, pressure ain't enough to push it past the water pump and give you a good stream of water, at the ball gears from the water intake.

Don't know about that side one i seen them, don't know if will give you a stream of water without the motor running.

Would you be so kind as to post the result if you try.
 

MrLundt

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Re: Impeller prediction... will it work?

Thanks for not scolding! There's no water intake on the side like my outboard. Manual says the "cooling water pick-up" is on the bottom of the lower unit, right above the spinning prop and right in front of the "rudder trim tab and exhaust outlet".?. I can see no way of getting muffs near that. The hose attachment is pictured in many or the manual's illustrations but never labeled. I guess I'll just see what happens??? and will definltely post the results.
 

NW Redneck

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Re: Impeller prediction... will it work?

The hose attechment on one of the pivot end caps is where to hook your hose when running out of water. It is not the best way to determine if the impeller is working however. The pressure from the hose can force water through as is the impeller is good. Either put the leg into a large drum with the hose going into the drum to leep it filled, or put the boat in the water. With the engine idling, remove the hose from the intermediate housing to the engine t-stat housing and see how much water flow you have through it. You should have a heavy stream of water if the impeller is good. Low volume or just a trickle or sputter means impeller is toast.
 

MrLundt

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Re: Impeller prediction... will it work?

Thanks for the help! I'll give it a try and let you know.
 

MrLundt

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Re: Impeller prediction... will it work?

The hose attachment on one of the pivot end caps is where to hook your hose when running out of water. It is not the best way to determine if the impeller is working however. The pressure from the hose can force water through as if the impeller is good...

It is true... The hose attachment fills the system w/ water d/t the pressure from the faucet. No way to tell if the impeller is working that way and I don't have a drum large enough to test it that way. I'm about to take it to the lake to see if the impeller will do it. Will likely stay very close to the dock in case of overheating. May not even untie. I'll let you know...
 

Fishermark

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Re: Impeller prediction... will it work?

As you noted, the old OMC outdrives have the water pickup in a different place than most outdrives and require a different "muff." I don't know if you can still buy the right adapter for the water intake at the bottom or not - but they DID make them. The old Chrysler outboards had a similar arrangement if memory serves me correctly.

Also, again as you noted, you can screw your hose directly into the side at the adapter for normal flushing, but that will not tell you much about the condition of your impeller. Why not simply replace the impeller and be done with it instead of taking it to the lake and trying it? It is going to need to be replaced one way or another.... either because it is simply old and needs to as a regular maintenance item, or because it is damaged.
 

Uraijit

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Re: Impeller prediction... will it work?

+1

Just replace it, and forget it. Even if the impeller is still functioning now, it's a time bomb. It's gonna leave you stranded, overheated, or worse.

Over a $20 part? :confused:
 
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