# engine swaps?



## goldxlt

hi i have craftsman lawn tracter with a 17h ohv(briggs and stratton) engine that is just about done however the tractor is in great shape; figured the best option was to replace the motor but i am having trouble locally finding a used 17hp motor. for whatever reason i am finding lots of 20 hp briggs and i was wondering how much of a pain it would be to use one of these motors?


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## dangeroustoys56

It depends how big the motor is and how the exhaust is configured - the electrical and stuff can be changed to fit it.

Id mesure the underside of the hood to its widest points and the depth as well - then when looking at the replacement motor measure from the bolt flanges to the top of the motor and side to side - if itll fit under the hood , it should swap in - most tractors have multiple pre drilled bolt patterns for multiple displacement/ different manufacturers. If it has an oil filter that might interfere - a remote oil filter locator ( from auto parts store) could be used .


Ive done plenty of lawn tractor motor swaps - i put a '96 18HP twin on a '94 murray that originally had a 14.5HP OHV motor - fit like it was ment to be there.

I also swapped a 13HP briggs onto a 99 murray with a blown 12.5HP briggs - i had it apart and back together and running in a half hour.

The only other thing is the crankshaft diameter- if the 17HP has a smaller crank then the 20HP- youll need to find a drive pulley the same size as the 17HP but with the bigger shaft size- with stock mowers you dont want to be changing the drive ratios- make sure you measure the crank diameter as well - a mower parts place should be able to come up with a similar pulley with the larger crank size- if its needed.


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## wjjones

goldxlt said:


> hi i have craftsman lawn tracter with a 17h ohv(briggs and stratton) engine that is just about done however the tractor is in great shape; figured the best option was to replace the motor but i am having trouble locally finding a used 17hp motor. for whatever reason i am finding lots of 20 hp briggs and i was wondering how much of a pain it would be to use one of these motors?


 If you can find one off of another craftsman parts mower it should fit perfect, and wire up too..as mentioned the crank pulley will need to match for the drive belt, and deck belt to line up. Does it have manual deck engagment or electric pto?


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## goldxlt

it has the manual deck engagement. i would have never thought of the crank pulley, thanks for the help


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## Mickey

Do you know the series the old engine is? If known you can go to the B&S site and DL the manual for it and from that you should be able to get mounting bolt pattern and other useful information. With that you can compare to a replacement engine. A similar size engine even from different mfgrs could have the same mounting bolt pattern. Big issues will be physical dims, i.e. will it physically fit under the hood and is exhaust is a similar location to the point where it isn't an issue.

Looking at current Itek engines, all of them from 15.5HP to 19.5HP have same displacement and I suspect they are all the same physical size including mounting.


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## wjjones

goldxlt said:


> it has the manual deck engagement. i would have never thought of the crank pulley, thanks for the help


 So the crank pulley will have to be a double pulley. Where are you located, and have you checked your local CL?


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## goldxlt

im located in ny, i have checked craigslist, mostly found 20hp motors, fittting size was wasnt to much of a concern, i was just a little worried if the rear end wasnt up for the power or if the pullys would hav to be changed.


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## wjjones

goldxlt said:


> im located in ny, i have checked craigslist, mostly found 20hp motors, fittting size was wasnt to much of a concern, i was just a little worried if the rear end wasnt up for the power or if the pullys would hav to be changed.


 The rearend will hold just fine as long as your pulley configuration works which i am pretty sure it will. I say this as long as its off of the same type of tractor the engine should bolt right up, and everthing should be able to be swapped over.


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## dangeroustoys56

Its only another 3 HP- as long as the motor pulley is the same as the original - it should be fine. Youd start getting into issues when you change pulley sizes - like if the trans one went smaller and the front drive went larger - then youd be getting into speed racer territory.

You probably wont see much of a difference in power actually - i have a 13HP older motor ( flathead) and a 16HP newer motor (OHV)- the 13HP is actually more powerful.


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## wjjones

dangeroustoys56 said:


> Its only another 3 HP- as long as the motor pulley is the same as the original - it should be fine. Youd start getting into issues when you change pulley sizes - like if the trans one went smaller and the front drive went larger - then youd be getting into speed racer territory.
> 
> You probably wont see much of a difference in power actually - i have a 13HP older motor ( flathead) and a 16HP newer motor (OHV)- the 13HP is actually more powerful.


 Good point dangeroustoys56 i had forgotten about the pulley diameter needing to match as well.


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## goldxlt

i picked up a 20hp briggs to put on it, i really havent had an opportunitie to play with it but looks like it will bolt in with no problem, the exauhst might take a little reworking but other than that i think it will work just fine.


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## wjjones

goldxlt said:


> i picked up a 20hp briggs to put on it, i really havent had an opportunitie to play with it but looks like it will bolt in with no problem, the exauhst might take a little reworking but other than that i think it will work just fine.



Good to hear keep us updated..


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## goldxlt

ok small update, i have been busy with so many things.

i finally got the old motor out and the new one put up and quickly found out that it is a lot larger the the old and that it wont be a direct bolt up; the holes in the frame do not line up with the motor, provided i have the motor sitting in there correctly.

old









new









the hood does close










i have to make some new mounting holes and i was going to try and make it so the shaft will drop down in the same position as the old so that i can re-use the belts, here is very roughly how it will be sitting, it seems close to the tank but i have some room to slide the tank back if you all think i should



















as you can see here, the pullys are spaced a little differently, overall they are the same height and the pullys are the same diameter, its just the top pully. the old one measures 5 1/16" and the new 5 3/16". think it will make enough of a difference? should i run the old one that came on the tractor?









provided i have the engine positioned properly, everything should connect up fine exept for the throttle, the old motor had the carb on the left side (sitting on the seat facing forward) and the new motor has it on the front, pretty sure it wont reach around the front.


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## dangeroustoys56

Id move the gas tank back at least an inch or so from the flywheel shroud - it could wear a hole in the tank eventually just from vibration.


About the pulley- it depends where final motor placement is going to be - id try n use the original one if it fits - it wouldnt make that much of a difference with a hair bigger pulley tho. Original is best.

Youll most likely need to get a new throttle cable and choke cable for a twin cylender - those are long enough to stretch .

Possibly the reason for the mis matched motor mount holes is an option is a OHV twin - those have different bolt patterns then an opposed twin- personally speaking the opposed motors are way better then OHV twins - built stronger and more power.


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## goldxlt

cool thanks


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## goldxlt

had a little time to work on it this morning, i drilled new holes for the motor to mount in and have it all bolted up, i am making progress but i still i was hoping it would have been more of a direct bolt in. i got looking at the electic hook ups and they do not match, is there a site i can go that has some sort of electrical diagram so i know what it all is or am i better off folling the wires to their point of origin?










the one on the left is from the motor, right is the one on the tractor


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## BelarusBulldog

You are going to have to cut and splice one of the plugs. Trace back the wiring to see what each wire does and make the right connections.


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## dangeroustoys56

The 3 off the motor possibly are : a stator feed wire, power wire for the lights and the magneto kill wire- depends if the motor has a antifire solenoid or not ( late model motors have them ) might also be one of them if the lights are wired direct.
If you still have the old motor, itd be easier to trace where they go - if the new motor doesnt have the solenoid , then it doesnt need to be hooked up.


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## goldxlt

yeah i got the old motor around, i will trace those wires back then, thanks for the help


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## goldxlt

dangeroustoys56 said:


> The 3 off the motor possibly are : a stator feed wire, power wire for the lights and the magneto kill wire- depends if the motor has a antifire solenoid or not ( late model motors have them ) might also be one of them if the lights are wired direct.
> If you still have the old motor, itd be easier to trace where they go - if the new motor doesnt have the solenoid , then it doesnt need to be hooked up.


ok well i thought i traced everything good but i can not get it to turn over. i have the wire from the coil hooked up correctly and the two wires from the stator feed? hooked up. for those last two i figured it was safe to assume that red was positive and black was negative on both the motors so i did red to red and black to black. on the "old" harness from the tractor (was hooked up to a newer motor) i have an extra wire that originally ran to the bottom of the carb; (antifire solenoid?) and seeing how the replacement motor(older motor) did not have this i just left the wire hanging. any ideas? should i do somthing with this extra wire? ground it out or somthing?


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## Mickey

For the heck of it I pulled out several old service manuals for B&S engines. Brought back some memories. B&S had numerous electrical schemes over the yrs and engine models. There were A.C. only output, D.C. only output and a mixture of A.C. & D.C. In addition there were various current ratings.

Think the safe, best, thing to do is determine which electrical scheme the old engine and chassis had and compare that to the electrical scheme for the replacement engine. from that, one should be able to come up with what is needed to make replacement engine electrical system work with the chassis wiring.

Have model numbers for both engines? My books aren't new enough to cover the newer OHV engines. Do have some info for the flat twins but think they are for models older than what you have but possible electrical scheme is the same.


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## goldxlt

i have the twins model information, model # 461707 and the type is 0145E3. i dont have any numbers on the the other motor handy. i will certainly check all that out, certainly not somthing i had thought about. thanks for the information.


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## goldxlt

ok after spending hours trying to under stand wire diagrams i finally put them side to side and i see the the tractor i am putting the motor on has an antifire solinoid and the "new" motor does not. the anti fire solinoid has a lead comming in and and then a lead comming out. when i hooked up the new motor i just left the lead from the tractor for this solinoid hanging but now i think i have to close the loop. im going to look over the motor i took off and see where the lead leaving the solinoid goes and see if ican find an easy way to close the loop off


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## wjjones

goldxlt said:


> ok after spending hours trying to under stand wire diagrams i finally put them side to side and i see the the tractor i am putting the motor on has an antifire solinoid and the "new" motor does not. the anti fire solinoid has a lead comming in and and then a lead comming out. when i hooked up the new motor i just left the lead from the tractor for this solinoid hanging but now i think i have to close the loop. im going to look over the motor i took off and see where the lead leaving the solinoid goes and see if ican find an easy way to close the loop off



Yep that should do it i would think it is causing an open ground??


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## dangeroustoys56

No - the antifire solenoid only was a fuel shut off valve - i unhooked mine on my 94 murray when i bypassed it and it didnt have any effect on how it ran. I cut the wire and just left it ( well taped it off from the switch side).

The motor does run- right? If the starter is hooked up- just temporarily unhook the other wires and try firing it up - itll run w/o those too. 

If it does run- then something was goofy with the wiring.

One of the wire diagrams i found with 2 leads from a stator shows red ( contains the diode) going to the ign switch/starter solenoid ( positive side) - the black wire is for the headlights ( goes to the ign switch for the lights) or the 'run #1 ' position.

The magneto ground wire is routed thru the saftey switches before attaching to the ign switch.

Hope this helps y out.


I do have to say wiring is a serious pain - most of mine were so hacked up so bad anyway i started over fresh - technically all that needs to be hooked up is the stator wire to charge the battery and the magneto ground. 

My briggs antifire solenoids only had one wire going in - on another wire diagram it shows the antifire solenoid is hooked into the ground /saftey switch system .


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## Sledge740

The Orange wires should be the kill wire. If you trace it it will go to a lot of safety switches. Most of those are normally circuits. Blue wires are normally closed circuits.


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## goldxlt

well its a good question if it will run, but i can get the starter to engage of i take my battery booster to it so i know i should be able to get that. i have everything hooked up correctly, didnt make any difference if i grounded out the antifire solinoid wire. the tractor did work before winter so i am assuming that everything is allright. could be my problem, i am going to go through all my connections and make sure everything is clean


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## goldxlt

ok little update and boy is my face red, turns out it was a simple as a bad fuse, the worst part is i pulled the fuse out days ago to check it and it didnt look blown to me, put a new one in and now the starter cranks, now all i have to do is put it all back together and i ought to be ready to mow just in time for all the rain:dazed: oh well, thank you every one for you suggestions


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## wjjones

goldxlt said:


> ok little update and boy is my face red, turns out it was a simple as a bad fuse, the worst part is i pulled the fuse out days ago to check it and it didnt look blown to me, put a new one in and now the starter cranks, now all i have to do is put it all back together and i ought to be ready to mow just in time for all the rain:dazed: oh well, thank you every one for you suggestions



I have done the same thing hundreds of times its always the little things that get missed.. We are all here to try, and help together  Keep us updated..


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## dangeroustoys56

Sometimes can be the simplest issue.....


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## Sledge740

I just swapped a 14 hp Tec. on a Murray with a 20 hp Tec. from a Yard Machine. The bolt holes were there. I had to change the main shiv and I used the wiring off the old YardMach. I had to move the hood forward because of the exhaust. Runs and cuts great and will get you down the road a little faster.


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## goldxlt

thats cool, i was originally hoping this was going to be more of a bolt and go, probably would have been for somebody who knows what they are doing.

new problem i have is fuel delivery :argh: if i have the tank sitting in normal position i cant get fuel to the carb, the bottom of the tank is lower then the carb. i took the tank off and just held it above the carb and it would run so i put the tank back into its mouting place and put some spacers to lift it up above the carb but again it wont feed. the line does drop below the carb but i figured that if the tank was higher it would still work. the tractor this came off of had a the tank below the seat, there is no way that is higher then the carb, do they have some sort of fuel pump? could i get an inline fuel pump?


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## Mickey

Fuel pumps are common for these kinds of engines. Surprised if the replacement engine doesn't have one.


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## dangeroustoys56

All my opposed twin briggs either have fuel pumps cast directly into the front of the carb or a manual pump somewhere under the hood to get a vacuum pulse from the motor- you can get fuel pump rebuild kits all you need is the motor number and how many bolts the pump is ( usually 3-4 bolt) . Pull the air cleaner assembly off and double check. Its right where the fuel line hooks into it.

An alternative for a fuel pump would be one off a older snowmobile- a simple pulse type pump . 

Yepper- big twins are thirsty devils - they need alot of go juice.


To make sure the fuel is flowing on my tractors - i replaced the last section going to the carb with clear fuel rated tubing so i can glance and see.


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## goldxlt

dangeroustoys56 said:


> To make sure the fuel is flowing on my tractors - i replaced the last section going to the carb with clear fuel rated tubing so i can glance and see.


thats a good idea. 

i didnt know about the fuel pumps built into it, how does it work, i dont have any sort of electrical going to it?


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## wjjones

goldxlt said:


> thats a good idea.
> 
> i didnt know about the fuel pumps built into it, how does it work, i dont have any sort of electrical going to it?


 I think it runs off vacuum from the breather? Its been awhile since i worked on one of these, and i cant remember where it gets the source for vacuum from..


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## Mickey

These kind of pumps typ work off the pulsating crankcase pressure.


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## goldxlt

well thanks for that, i went out and figured it all out and now it mows kindof i just have to get a manual choke cable, right now i have it rigged up with a coat hanger and then do some throttle adjustments


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## dangeroustoys56

Cool beans- glad its running for you.

The fuel pumps are pretty simple- basically 3 springs and a flexible rubber membrane (ones cast into the carb) - the pulse hose is mounted to a barb fitting on the front of the motor- you want to make sure this hose is in good condition ( no cracks) and has clamps on it for a good vacuum source.


My big horizontal twin on my GTII has the factory pump disabled and a rather large remote pump mounted on the 'firewall' - that still uses motor vacuum- probably has to be bigger since its drawing fuel from the back of the tractor.

An electric pump would be overkill for a lawntractor, some sort of pressure reducer would be needed.


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## wjjones

goldxlt said:


> well thanks for that, i went out and figured it all out and now it mows kindof i just have to get a manual choke cable, right now i have it rigged up with a coat hanger and then do some throttle adjustments



Whats wrong with the coat hanger??...... Glad to hear your getting it worked out keep us updated..


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## wjjones

Mickey said:


> These kind of pumps typ work off the pulsating crankcase pressure.



Thankyou Mickey i knew it was something like that just couldnt remember... cause of my sometimers....


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## goldxlt

wjjones said:


> Whats wrong with the coat hanger??...... Glad to hear your getting it worked out keep us updated..


haha it needs to be wife friendly

as for my vacuum hose, i am using an old piece of fuel line for now, has some cracks starting and no clamps, i plan on getting something better put on in the next few days, should i stick with fuel line or can i get some plain jane clear hose?


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## parapower

go to partsnationwide.com
they have just about any mower part or engines u need
or try outdoordistributors.com

if u can find the same engine type u will not run into any modification problems


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## dangeroustoys56

Just regular rubber vacuum hose works - all that goes thru it is air.


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## jhngardner367

Hi,guys!Sorry I didn't get back to the sight sooner,but my computer destroyed itself,and I just got everything going, again!I really missed all the posts,the last couple of months!


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## wjjones

jhngardner367 said:


> Hi,guys!Sorry I didn't get back to the sight sooner,but my computer destroyed itself,and I just got everything going, again!I really missed all the posts,the last couple of months!



No worries Welcome back...


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