Could be a bare wire in the mower deck circuit! Maybe, by connecting the charger backwards, it made a wire get very hot, melt its insulation, and then it would short out when you try to make the deck run. And no, i don't think it is that switch, although anything is possible. It'd be better to check the wiring to the PTO! And better hope it ain't the PTO, as they are EXPENSIVE!

OK, we need the Sears model # from the chassis sticker. Sticker may be under the seat. Number needed begins with 917. xxxxxxxx. Providing that number will allow us to view a manual online to determine how the machine is wired and the type/brand of engine. Once we know the configuration of the charging system, we can better determine the possible faults.

the model # 917. 274641

Ok, you are going to have to unplug some specific wire connectors in order to determine exactly what has gone zzzzzzzt when the battery polarity was reversed. First though, could you tell us how many amps your battery charger was set for and how long did you actually try to charge the battery backwards? Or is this a big charger/boost start unit and you had it on "Boost start"?
You are ideally going to need a volt/ohm meter, or a combo multi-meter to do some of the tests. If you don't have one, and want to continue with the tests, you need to go somewhere and buy a cheap one. Can be found everywhere automotive stuff is sold, even wallyworld. I'll work up a few things for you to check after I look at the circuit diagram more tomorrow morning.

the charger was on 10amp for about 2 hrs, then up to 30amp when the start was attempted. I have a multi-meter that will work. thanks

CM, you can delay getting the voltmeter (at least for now) because having studied the wiring diagram, I believe the problem is in the voltage regulator/rectifier unit. This small module is attached to the outside of the engine sheet metal (don't know exactly where). Look on page 50 of the owner's manual at item # 501, that will give you some idea of what you are looking for. Find that part on the engine and unplug it (just as a test). With the voltage regulator unplugged, start the engine and try to engage the PTO. If the engine keeps running strong without stuttering and dying or blowing the fuse, you have isolated the problem. You will need to replace the damaged voltage regulator. Because this part is offered by Briggs, you can find it at small engine shops that service B&S engines, or you can go to Sears.
If, the engine continues to behave badly with the regulator unplugged, the next thing to unplug (for testing) is the wire that connects the PTO clutch to the tractor wire harness under the tractor. With this wire unplugged (and pulled safely away from the PTO), start the engine and pull the PTO knob to the engaged position. If the engine now runs strong without blowing the fuse, the PTO clutch is defective, and will have to be replaced. If the engine continues to behave badly after this, we will need to go into some other areas. I think you'll find the problem in the voltage regulator. These units can be "zapped into oblivion" by connecting a booster battery or battery charger backward (reversed polarity). Sometimes the only problem that occurs after a reversed polarity event is that the battery no longer receives a charge from the engine alternator, so you don't get the blown fuse and the "will not run" symptoms, all you get is a battery that runs down (with all the symptoms of a dead battery, naturally). Sometimes though, a regulator/rectifier, or even the simpler plain diode rectifier, will create a "short", instead of an "open", inside the unit. When this happens, you usually have fuse blowing complaint, in addition to other stuff, depending on the individual machine.
Check this out and let us know what you find.

Here is a link that might be useful: 917.274641 OM

Ok, I unplugged the volt reg, started the engine, engaged teh pto, and the engine continued to run normal. I disengaged the pto and the engine quit and the fuse was blown.

You have some extra fuses I hope. When you engaged the PTO, did the mower blades operate normally? Have you tried the other suggestion to use the ROS position of the key switch to see if that will allow the engine to continue running? You don't need to actually have the transmission in reverse, just have the key switch in the ROS position. Did the engine quit while you were pushing the PTO knob in, or did it quit a moment after the knob had been down? Probably going to be tomorrow before I get back onto the forum.

when I engage the pto, blades remained motionless. I did try the ROS position and it didnt seem to affect anything.

The engine quits after a moment while the PTO switch is out, if I'm quick enough I can push the switch back in and the engine will resume to run normally.

The schematic is on page 33/56

The wire to the PTO goes through the "center" terminals of the PTO switch.

You might try disconnecting the wires to the PTO itself and checking it for a dead short.

There should be about 3 OHMs through the PTO windings. (you have to exercise a bit of care measuring, because at that low resistance, you are also measuring the resistance of the test leads)
IF you have that, the problem appears to be that the wire is shorted between the PTO switch and the PTO.
IF you have ZERO OHMS THROUGH THE WINDINGS, the PTO is shot.
IF so, you shouldn't blow a fuse with the PTO wires disconnected.

I'm not totally understanding everything you mean. I did disconnect the harness behind the pto switch and tested the terminals on the harness and came up with about 1.3 or 1.5 OHMs. The tractor wont start at all with this harness disconnected.

Get under the tractor and unplug the wiring that leads into the PTO clutch. Use your Ohm meter by touching one lead to the unplugged wire that goes into the PTO clutch while touching the other test lead to a clean, bare metal place on the engine or chassis (unpainted head of a bolt is good). Then, as bill stated, a reading of about 3 ohms resistance would indicate that the ohm meter was detecting a good and continuous circuit that runs all the way through the 3 miles or so (actually an exaggeration of distance) of copper wire in the clutch coil. If you get an Ohms value of zero, that means either the coil windings, or the anti-spike diode inside the clutch, have shorted to ground. Either of those defects will give a zero resistance reading, which is analogous to simply touching the two test leads together.
I hope that makes some sense of what you are trying to measure

Well I unplugged the connector to the pto clutch, there were 2 terminals. I put a lead on one of those (clutch side) and then tried various gnding pts with the other, I even tried the negative side of the battery, each time I only got 0 OHMs. I did put each lead on a terminal on the connector and got approx 1.5 OHMs, if that means anything.

***"I did put each lead on a terminal on the connector and got approx 1.5 OHMs, if that means anything."***
CM, I should have included the step that you did above.
But, when you state that you were "getting zero ohms" on some of the ways you connected the meter, do you mean that you actually watched the meter pointer (or LCD if digital) drop to zero? Or, are you saying that the meter reading "did not change" when you touched the tester leads in those configurations?
But, getting back to a specific suggestion (which you have not "answered" yet)..........have you tried running the engine with this 2 wire connector unplugged from the PTO?
If you have not done that yet, do that now. Unplug the 2 wire connector, sit in the seat and start the engine, engage the PTO. If the engine continues to run, this pretty much confirms the PTO clutch assembly is defective. If, the Ohms value of 1.5 is an accurate reading (from when you tested across the 2 terminals of the PTO wire pigtail), that is too low and indicates a defect in the PTO. If this is confusing (zero ohms is not the same as "zero indication"), maybe this will help. Ohmeters use a battery inside the meter to send current through the test leads. How well the circuit is able to conduct this tiny amount of electricity is a good indicator of the health or status of the circuit being tested.
When you turn on the Ohmeter and the test leads are not touching anything (hanging in the air), the reading you see on the meter face IS NOT zero Ohms. It is "zero indication", also known as "infinite Ohms" or simply "infinity". That just means that the resistance the meter is detecting (it is trying to measure the resistance between the two test lead ends) is much too high to register, so the meter calls it "infinite resistance", because no current is flowing in the test circuit, which at the moment, is the air gap separating the 2 test lead ends.
When you touch the 2 test leads together while watching the meter face, you should see the reading change. If you have an analog meter, you will observe the pointer or needle move from one side of the scale to the other side (usually it moves from right to left). If you have a digital Ohmeter, you will observe a flurry of activity in the display window as the meter negotiates to deliver the new reading (caused by touching the leads together).
How does this relate to this PTO? The PTO uses a coil of copper wire to create a very powerful electromagnet whenever 12 volts is applied to the wire coil. A very long wire is used to construct the coil. Because of the length & diameter of the wire, it is less than a "perfect conductor" of electrictity, and exerts "resistance" to the flow of current out of the Ohmeter battery through one lead, and back into the meter on the other lead. This resistance is "Ohms". Inside the PTO, there is a diode. This diode has nothing to do with the the actual operation of the PTO! It is in there to keep the coil from returning a voltage "spike" back to the PTO switch on the dash whenever the PTO is being turned off (like when you want to stop the blades from spinning). Diodes are "polarity sensitive" by their very nature. In fact, that is exactly how and why they are used for certain electrical functions. When you reversed the polarity of the battery charger at the beginning of this adventure, you probably destroyed the anti-spike diode in the PTO, causing it conduct current in 2 directions, instead of just one as it was designed to. The PTO Ohm reading for a "good" PTO should be something between 2.4 and 2.9 Ohm when the Ohmeter leads are connected across the PTO wire terminals, using the correct polarity. If you reverse the test lead polarity, the reading should change to around 1.5 Ohm or less. If the Ohmeter reads 1.5 Ohm regardless of which way you connect the test leads to the terminals of the PTO pigtail, the PTO is defective.
Or, just unplug the PTO pigtail and run the tractor with the PTO switch in the mow position to see if the fuse continues to blow.

well I went back and re-checked the OHMs. I get no indication with one lead on a terminal and one on a grnd. I do get 1.5 with both leads touching each other, and 1.5 with a lead on each of the terminals to the clutch, and even when I switch the leads (ie...both directions of current). with the clutch unplugged, I sat and started the engine, engaged the pto, engine continued to run normally and did not blow the fuse. So I'm guessing I need to drop the pto clutch and replace it. doesn't look to tough of a job...

Before you install your new PTO (provided your loan is approved) check the pigtail terminals as in the tests. I believe you will see what I mean about the difference of Ohm reading when the polarity of the meter is reversed. Now, if only that regulator/rectifier has survived!!!!!!!!!!! Stay tuned to this station.

ok, so much for it being an easy job. I'm trying to remove the clutch. I undid the 3 nuts around the clutch, but I'm having trouble getting the nut off the end of the pully, which the shaft appears to be connected to the engine (which makes sense). How do I get that nut off?

Lets pretend the image below represents your PTO. Do the RED Xs match up with the 3 nuts you mention? Does the Green arrow point to the "nut" (How do I get that nut off?)
at the end of your post?
What looks like a "nut" is actually a bolt (the bolt) holding the PTO center hub to the crankshaft (engine).
The preferred (by all who need it off) way is to use an impact wrench. If you don't have one, you can do the "Po boy" trick and hold a boxed end wrench on the nut and strike the other end of the wrench really quick with a hammer. I recommend wearing some good leather gloves while doing this (because you never know "what" you might hit with the hammer besides the wrench). The bolt come loose by turning it counterclockwise (if you were looking head on at the bottom end of the crankshaft). You may have to strike it several times, repositioning the wrench if the engine turns. It is very important to keep the boxed end of wrench seated firmly on the bolt head while hitting it with the hammer to keep from damaging the head (of the bolt). Sometimes, it is better to "tag team" this operation having a helper hold the wrench in place (gloved hand please) from one side of the mower while the hammerer does the hitting from the other side (gloves please).
Once the bolt is removed, the PTO might fall off easily, so be careful it doesn't hit you. Or, you might have to tap around on the pulley with a hammer to "jar" it loose. Good luck with this!
{{gwi:348022}}

yes, you are exactly correct. I'll try it on sunday. thanks

I forgot to include that those 3 small nuts.........are not part of the PTO removal procedure. Those nuts only need to be "messed with" if the air gap of the PTO needs adjusting. There is an "anti-rotation" key mounted to the frame (view it on page 38 of the OM, item # 23). Make absolutely certain that you pay attention to getting the PTO oriented correctly over this key when you are installing the new PTO. Pay equal attention to where the wire pigtail routes away from the PTO and toward the mating connector on the chassis harness. If you get the pigtail oriented at the wrong "clock position", it will not reach the chassis plug and have enough slack to route away from the clutch. If you miss the antirotation key, the PTO assembly is liable to spin upon engagement, and there go your new PTO $$$ right down the drain. See the image below. There are some other configurations of anti-rotation brackets used on different types of machines, but I found this drawing to cover this thread issue.

{{gwi:348023}}

thanks. got the clutch off and new one and new belt is on the way by friday. I'll take a look at the anti-rotation bracket.

DO NOT crank the engine until you double check the anti-rotation bracket locator. Even without a belt, damage may occur (though not nearly as certain as with a mounted belt).

ok, got the parts in, I'll thread the belt in first then attempt the clutch

got the belt and clutch on, with the anti-rotation bar in place. Went to hook up the clutch wiring harness and found out it has different connectors than my old one. Called sears to verify I have right part and asked her if I could use old connectors, which she said I could. So I guess I'll splice in the old connectors. commments??

The easy way is to use the old connector. Cut the old wire pigtail loose from the old clutch near where the wires disappear into the clutch. Then, take this lead under the tractor and plug it into the OEM connector on the chassis wire harness. Bring the new clutch wire pigtail around and lay it over the length of the old pigtail. Study this situation to be sure you are not cutting off too much wire from either pigtail. You want sufficient length of the new pigtail (old plus new wires) to route the pigtail away from the clutch, but not so much length that you worry about the excess getting back into a belt or a pulley groove. With all 4 wires (2 old, 2 new) bunched together after deciding where to cut, cut across all 4 wires at once, or at least, at the same location. The wire ends can now be spliced together using heat shrinkable coated butt splices (crimp connectors). Or you can use solder and heat shrinkable tubing to seal that. If you use separate heat shrink tubing and solder, be sure you slip the tubing onto the wire and away from soldering heat BEFORE you solder the splice. Or, you can buy ininsulated crimp butt splices and use separate heat shrink tubing to seal those. Same precaution as for solder, put the tubing over the wire before you crimp.

thanks, but does it matter how the wires are plugged in. There are 2 wires and does it matter if they are reveresed or not? The old connector has 2 male plugs, similiar to a
house electrical cord,(1 horizontal and 1 vertically positioned from each other) the new connector has 2 small round metal tips (cone shape). I just want to make sure that it doesn't matter how the wires coming from the clutch match up to the wires from the tractor.

Should not matter. If it was critical, one of the wires would be a different color. I have never seen polarity mentioned with these clutches.

Thanks Mownie. I got it all together and everything is working fine. I guess I'll be a little more careful next time I put the battery charger on it. Thanks again

You are welcome and I'm glad to hear the successful results. Yeah, by all means be very careful about the polarity when charging or "jump starting" batteries. Use red paint, red tape, or other effective means of marking the positive side of battery and cables so they are as conspicuous as possible. Do the same to your battery charger and jumper cables.

Well, we would like to look at the owner's manual. Could you post that 917.?????? number please?
And take a look at another scenario involving reversed polarity. If you have multiple batteries that you like to swao around, you better get 'em all marked up with red on the positive posts and cables, I promise, that's cheaper.

Here is a link that might be useful: Bad polarity, bad news

I got my polarity reversed! The above was for another thread I was juggling.