Replacement Engine for 28V707

ponyakr

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I have a Murray WideBody LT rider with a B&S Model 28v707, Type 1113-E1 Code 991001ZD 12.5hp engine.

It appears to have a broken crank. I'm not a small engine guy. But, the rest of the mower is still in good shape. So, my question is: Is there a simple bolt-in replacement engine for this mower ?

I Googled it. Found some new B&S 12.5hp vertical shaft engines. BUT, I have no idea if any of these are direct bolt-in engines, since they all look different than the old engine.

Have quite a bit of mechanical experience with older car engines, but none with small engines. i think I can replace an entire engine, if it's a simple bolt-in.

The mower is older & therefore not worth the price to pay a local shop for a new engine swap.
 

cpurvis

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The Briggs & Stratton website used to have a 're-power' section. Have you checked that?
 

ILENGINE

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Briggs dealer site shows the 219907-3026-g5 superceded to a 21R807-0072-g1 to replace your current engine.
 

ponyakr

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Yeah, I'd looked that one up.

(1) Anybody know what other parts I'd need to buy new ? Starter ? Muffler ?

(2) So, has anybody here done this exact replacement ?

(3) Direct bolt-in ?

Sorry, but this is my first attempt at anything like this.

1st prices i looked up were well over $500. Anybody know the cheapest place to order one of these engines ?

The rest of the mower is in good shape. But, I don't know if it's worth a $500-$600 investment.

How about a rebuilt shortblock, like you can buy car engines ? Again, sorry for the dumb questions. But hey, if you don't know, you just don't know.
 

bertsmobile1

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Any single cylinder Briggs engine from a riding mower will drop right in .

Look at
The surplus centre
Small Engine Warehouse
Small Engine Suppliers

These all sell surplus engines quite cheap.
At this time of the year you can often get brand new pulls because the mower company has gone to a bigger engine or changed brands.

NEw engines generally come drop in complete with starters & carbs.
Some have mufflers & fuel tanks , some don't.
Generally single cylinder engines with exhausts will fit.
At worst you might need to cut away the side of the hood a little or do some 10lb hammer fitting.
Engine mufflers are a lot cheaper than mower company mufflers ( volume thing )
If your mower has a gravity tank ( under dash ) then pumps are not needed, but won't make any difference.
If your mower has a tank under the seat you will need an engine with a pump.

All Briggs single cylinder alternators are interchangable so that can be swapped from the old to the new if they are not the same .
However most new engines have better alternators than the older ones
 
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ponyakr

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Wow ! That sounds TOO easy ! So, you're saying that most any single cyl vertical shaft B&S engine, anywhere from about 10.5 to 20hp, is pretty much a simple bolt-in, for my 12.5hp Murray lawn tractor ???

I'll check for those cheaper engines you mentioned.

Thanks !

Anybody else have any other sources for a cheap price ???
 

bertsmobile1

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Yes.
3 shaft diameters
7/8" , 1" , 1.125"

Yours will be 1"
Then there are a few different shaft lengths but most are 3 & 5/32 "
Engines are built around a bore & stroke so you will generally get up to 6 Hp ratings for each bore & stroke ratio.
Longer strokes will push the head further towards the front and the crankcase will be bigger which can make things like removing a gravity fuel tank quite interesting.
Bigger bores will move the position of the exhaust port & may also increase the size so you old muffler may not fit.

Just remember that the bigger single engines are LONGER so you can run into , or rather out of space, particularly for the muffler.
All mower engine run at basically the same speed 3500 rpm so a 20 HP engine will not go 1"/hour faster than your 12.5Hp engine and will use more fuel to boot.
Thus fitting a bigger engine is not really an advantage unless you are on a very hilly plot or regularly cut really tall grass that stalls out the engine.

The plus is because these are surplus engines the price is not directly proportional to the engine size so you might find a 17Hp engine that is cheaper than a 12.5 Hp engine.
The bolt on bits like controls & alternators ( stators ) all interchange as they have common mounting points.
You did not mention which Murray you have but most of the singles used a side muffler so just pick an engine that comes with muffler or another 280000 series so your muffler should fit.

Go to the last two site and you will see each engine will be described as being "exact replacement for ABC mower" or "replaces most 42' ride ons" etc etc etc

When the $ A was stronger to the $ US I would buy a few pallets of engines each season, generally what ever had the lowest $/Hp ratio cause it is easy to sell a customer a bigger engine.

Also note they come with 3 different lubrication systems
No filter , spin on filter , full pressure lubrication.
If you change your oil annually at the end of the season it will make little difference other than price which one you pick.
A pulled engine ( taken from an unsold mower ) will always be cheaper than a surplus engine and some are in short supply.
 

Texasprd

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My apologies for "necro-threading", especially with my first post - but the OP's situation was/is exactly the same as mine - Murray mower and the same model/type/code as mine.

What was the result on the OP's possible attempt to re-engine his mower? Did he go with the replacement engine model that ILENGINE found? (I know the OP was only in one other thread, and that was about the same time, so there may not be an answer from him...)

The OHV replacement model is 1-1/2" - 2" "longer" than the original "flathead" engine, by my measurements and the dimensions on Small Engine Suppliers and Small Engine Warehouse (assuming"length" is measured along the frame rails, like wheelbase). This seems to put the muffler and tube very close, if not into, the right-side good mount/hinge. Before I spend $400+ on a new engine, I'd like to know what the OP wound up doing (or if anyone else has done this with a similar (20 year old) Murray and engine model.

Thanks!
 
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Texasprd

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I went ahead and took the plunge - got a Briggs 21R807-0069-G1 from Small Engine Warehouse. Physically, it was a direct bolt-in.

Murray uses a mounting plate that bolts to the engine and frame - the nuts on the inside of the frame rail channels are difficult to get to. I didn't have any trouble with them on removal (stuck on from age?), but I needed a Ford/Chevy distributor wrench to get the nuts up in place and hold them while tightening the plate bolts from above. My distributor wrench is an old KD or Cal-van that can be separated in the middle to attach a 3/8 ratchet - perfect for this job. The throttle cable fits perfectly. Since the exhaust is on the other side, I did have to drill/cut a hole on that side of the hood - I recommend the equivalent of at least a 3-1/2 hole. That will take out the lower hood/grille screw, so be prepared to add a couple of screws near the remaining screw on that side to replace the cut out screw. I also removed the muffler guard - that may not have been necessary.

Electrically, there are a couple of wrinkles, but not bad. The 21R807-0069-G1 has a 5-/3-amp alternator, just like the original engine that the original poster and I had. The alternator harness, carb solenoid, and magneto-kill wire all wire into a 6-pin connector, of which four pins are used. I believe the connector is a Molex 50-84-2060 - if you want the matching plug to wire up on the mower harness, it appears to be a Molex 50-84-1060. I found them on Waytek Wire. If you look at pics of this engine, notice that the alternator output harness does not go directly into the Molex - it plugs into a short pigtail that then goes to the Molex. Because the alternator is the same as my old, I just disconnected the 2-wire alternator harness plug from the short pigtail coming off the Molex 6-pin and plugged the alternator output harness into the 2-wire receiving plug in the mower harness. The black mag-kill wire goes into the Molex 6-pin that comes on the new engine. A pigtail is available that seems to use the same single-pin connector as the original, but I didn't want to take the engine cover, flywheel, etc apart. I elected to cut the mag-kill wire where it entered the 6- pin connector, cut the receiver connector off the yellow wire in the mower harness, and crimp on 1/4" spade terminals (heat shrink insulated) to make the mag-kill connection. That left only the feed for the carb-solenoid. On my mower's wiring diagram, I saw no place that appeared to be a switched, positive connection that would be on all the time the engine is on (thus eliminating the momentary starter relay trigger). I would have had to run a separate toggle/rocker switch to activate the solenoid. I elected instead to remove the solenoid, cut the tip off with my Dremel, and reinstall. I did need a thin-head 1/2" open-end wrench for that, as my regular 1/2" open was too thick (to my surprise).

I know this is long, but I wanted to share what I was able to do, since I had exactly the same scenario as the OP.
 
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