How long can a motor run out of water before impeller damage?

[Commando C2]

Re: How long can a motor run out of water before impeller damage?

have you checked the rubber pipe that takes the water from the powerhead to the casing of the motor.
I bought an engine the other week.
the seller fired it up with no water to it as i got there. I was not impressed but it ran for 30 seconds then we stopped it.

I got the motor home put it in the barrel and only got a dribble of water from the telltale. New impeller i thought. then i checked the pipe and there was lots of grease and gunge in there. Cleaned it out and the engine pees out like a race horse.

If the impellor was wet then ran out of water it will prob survive. The seller of mine had it dry but it survived.

this is it pumping water once the blockage removed.
http://www.youtube.com/watch?v=uZuadzFkgIA

 

[emoney]

Re: How long can a motor run out of water before impeller damage?

Here's an easy rule to live by; "If you're looking at a motor from a private seller that starts it, without water, thank him and leave immediately." If he's done it for you, he's done it a number of times for himself. Commando, you got really, really lucky, but I would imagine the odds are against you. We still haven't heard how this thing fired up on it's own, have we?

 

[possom813]

Re: How long can a motor run out of water before impeller damage?

I think I figured out how it fired up, sorta.

The ignition system works funky, because we wired it from scratch with no idea how it was supposed to work. So we made it work.

To start the boat, there are two toggle switches that run to the magnetos and an ignition switch ran to the solenoid.

To keep from accidentally sending 12volts to the coils, we kept the toggle switches separate, with no power running to them. The toggle switches are there just to ground out the magnetos.

I found out a few days after it started on it's own that the motor would run on one cylinder if one switch was off and the other was on. I found that out accidentally.

When I think back, I seem to recall one of the switches being in the on position and I mistaken left the key in the on position.

Last Saturday, I took the boat out for the first test run and the starter engaged itself a couple of times and I had to turn the key off and back on for it to work right again.

So I'm thinking a combination of either a bad starter, bad ignition switch, and the one cylinder left on caused the mystery start. We'd had it running for a while just an hour or so before it happened, so it was still warm and ready to fire up.

Now it's got a new impeller and it does the same thing it was doing. The impeller in it wasn't bad at all, I wish I should have taken a couple of pics of it. It's supposedly been in the motor for about 3 months and it still looked good with none of the warping to it yet.

But now I know how and could probably do it again in 15-20 hours...

 

[fishndirk]

Re: How long can a motor run out of water before impeller damage?

Without being too rude, if you like wasting money than keep the electrical set up you have just described. Having your cylinders rigged up through toggle switches (especially seperate ones) is not a good idea. No boat, car, truck, generator, or lawnmower I have ever seen has had the ignition coils themselves ran through a toggle switch. Your creating multiple points of failure and in case your wondering, your magnetos (electro-magnets) will not generate any power unless the flywheel is turning (engine cranking or running). Spark plugs dont just accidently fire. So really the issue is keeping your starter from "accidently" energizing.

 

[Sixmark]

Re: How long can a motor run out of water before impeller damage?

I think I figured out how it fired up, sorta.

The ignition system works funky, because we wired it from scratch with no idea how it was supposed to work. So we made it work.

To start the boat, there are two toggle switches that run to the magnetos and an ignition switch ran to the solenoid.

To keep from accidentally sending 12volts to the coils, we kept the toggle switches separate, with no power running to them. The toggle switches are there just to ground out the magnetos.

I found out a few days after it started on it's own that the motor would run on one cylinder if one switch was off and the other was on. I found that out accidentally.

When I think back, I seem to recall one of the switches being in the on position and I mistaken left the key in the on position.

Last Saturday, I took the boat out for the first test run and the starter engaged itself a couple of times and I had to turn the key off and back on for it to work right again.

So I'm thinking a combination of either a bad starter, bad ignition switch, and the one cylinder left on caused the mystery start. We'd had it running for a while just an hour or so before it happened, so it was still warm and ready to fire up.

Now it's got a new impeller and it does the same thing it was doing. The impeller in it wasn't bad at all, I wish I should have taken a couple of pics of it. It's supposedly been in the motor for about 3 months and it still looked good with none of the warping to it yet.

But now I know how and could probably do it again in 15-20 hours...

OK I'm trying to pretend like I didn't just read what I did...............:facepalm:

With that being said, whatever you custom wired into the ignition system, UNWIRE IT What you have is not only completely wrong, it'a also a major accident waiting to happen.

Get an actual wiring harness for the motor/controls (if you haven't modified those too) and a manual and do it the right way. Or else you could put flahing yellow lights on it to let other boaters know that it's an accident waiting to happen.

 

[possom813]

Re: How long can a motor run out of water before impeller damage?

I've replied to the last two posts twice explaining everything that I failed to mention in previous posts.

I'm just going to sum it up this time and hope it posts.

The factory harness was used and the only modification were the toggle switches because we couldn't find, at the time, a 5 terminal universal toggle switch.

The universal starter switch we used was faulty, found out later when we recreated a similar incident, and had to have arc'd to send power to the solenoid.

It's all in the process of being replaced with a 5 terminal, marine grade, universal starter switch, just as soon as I can locate one.

 

[Sixmark]

Re: How long can a motor run out of water before impeller damage?

Well you might make it a little easier for us to help you, what type of motor is it? do you have OEM or aftermarket controls for it?, etc.

 

[possom813]

Re: How long can a motor run out of water before impeller damage?

1970 Johnson 40hp Electromatic.

OEM controls and harness

It uses a magneto ignition switch, I believe is what it is called, where it has two terminals for the magnetos to ground them out and kill the engine when the key is turned to the 'off' position.

It's on the way and will be replaced as soon as it gets here. When we wired everything up to make sure the motor was going to work the way it's supposed to, we did it the best that could be done given the equipment and parts on hand.