Engine swap on Ariens Zoom 34 model 915157

mbunch907

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Posting this because I could not find this information anywhere. I'll try and keep this short. I've had a zoom 34 for about 10 years now. I've never been happy with the 14.5 HP B&S (model: 31A507 0133 G5) motor that was on it. Fairly happy with the mower its self, just not the motor. It always bogged down in tall grass, had the shakes with PTO engaged, and was a routinely having maintenance issues. After 10 years of service it thankfully, finally failed. It seized up either due to a low oil amount, occasionally using automotive oil in it, or due to cutting on an incline and it being a splash lubricated system. Doesn't really matter, I was happy to start looking for a replacement. I decided to go with a Kohler V-twin Courage motor 20HP. Picked one up at Brandnewengines.com. They were easy to work with and had a great discount on the motor ($699). It still cost me $250 to ship to Alaska, but hey that's the cost of living in God's country. As it was being shipped I started researching what I was going to need for this change. To do this I researched the parts book for a zoom 34 (915157) but used the model size up because it originally came with a Kohler V-twin (model: 915159). To complete the install I needed a new Throttle cable and a new muffler. I also purchases a quick drain line for the oil plug and put it on before installing the motor.

In series: Old motor, motor removed, new motor installed.
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To change the motor:
1. Remove PTO (clutch) belt and the Drive belt.
2. Disco electrical: Remove connection to the starter, unplug wiring harness, remove ground, unplug PTO cable.
3. Remove bolt holding clutch on. Leave it where it is (between the two steering assemblies)
4. Tactfully remove engine mounting bolts. You'll have to use some ingenuity to get to the forward ones.
5. Disco Fuel lines. Keep elevated to avoid it draining onto your floor.
6. Lift engine out. You may have to use some tough elbow grease to get the clutch off of the engine. The clutch has a key that can easily fall out when removed. This key is necessary to install onto new engine.
7. Clean everything up. Use this moment to install some new belts.
8. Pre tap holes into new engine block (the bolts are self tapping, but a tap will work much better).
9. Toughest part yet. Line up new engine with clutch and its key. Get the clutch to slide all the way into the engine shaft with the key installed. It will probably take a few tries.
10. Slide engine ground wire into place between block and frame.
11. Install mounting bolts. This again will take some ingenuity.
12. Install fuel line. There will be one remaining fuel line that comes from the top of the tank. This was used as venting the tank into the head of the old engine. Its not needed for new engine to work, however your tank will still need to be vented.
13. Install muffler. Its important that you order the correct muffler. Otherwise it will not fit into the frame. Learned this the hard way, but the model 915159 muffler fits perfectly.
14. Install new throttle and connect it to the engine. New throttle needed because old throttle cable for the B&S engine will be too short.
15. Finish installing the clutch and plug in its electrical cable. If not already done, go ahead and install both belts.
16. Reconnect engine harness.
17. Double check everything. Wires, fuel lines, grounding, belts, throttle, etc.
18. Give it a go!

Initial impressions are awesome. It runs SO much smoother now and has zero issues going though thick grass. With the old motor I always thought that my blades were out of balance because it would shake so much. Not anymore! Hard to believe all of that came from the motor. Obviously its long term performance could be a differnt story, but for now I have a big grin :)
 

Scrubcadet10

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Good job! Hope it serves you well for years to come!
 

YodaMan

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Hello mbunch907, same 915157 Zoom34 as yours. Just locked up my motor as you did, last Saturday. So last night 5pm I came across your post and went ahead and pulled the old motor out, about 3 hrs, taking my time and also removed the flip up cover for space, yeh front 2 bolts were a knuckle buster. I was going to replace with another 15.5hp B&S replacement engine and I was quoted $1295 from dealer today, but I do get free shipping :), at that price I should get 2 motors. So now I am back reading your post and thinking I can do this with a little help from someone who has tackled the same project. My first time sending a message, not sure if it's going to everyone or just you, didn't want to bother everyone with my silly questions. Can we connect off line for a couple little tips that could save me trouble. I am not super handy but don't mind a challenge an you made this sound very doable, plus I have to do something. Are you will to go back and forth via email? or Even a call/text, never spoken to a true Alaskan before :). From Chicago so I would be conscious of the time difference. Appreciate all the help I could get. Thanks Anthony FYI aleycock@hotmail.com
Update: a couple hours later, I reached out to B&S headquarters and after a more in depth search they found a drop in 19HP motor for $637, so I pulled the trigger and will be installing sometime in the next two weeks. HQ had a 3rd part distributor reach out to me with details. I will see if i can post details as well as you did in another tread. Appreciate your post, it put me in the right direction and gave me the comfort to attack this swap.
 
Last edited:

mbunch907

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Hello mbunch907, same 915157 Zoom34 as yours. Just locked up my motor as you did, last Saturday. So last night 5pm I came across your post and went ahead and pulled the old motor out, about 3 hrs, taking my time and also removed the flip up cover for space, yeh front 2 bolts were a knuckle buster. I was going to replace with another 15.5hp B&S replacement engine and I was quoted $1295 from dealer today, but I do get free shipping :), at that price I should get 2 motors. So now I am back reading your post and thinking I can do this with a little help from someone who has tackled the same project. My first time sending a message, not sure if it's going to everyone or just you, didn't want to bother everyone with my silly questions. Can we connect off line for a couple little tips that could save me trouble. I am not super handy but don't mind a challenge an you made this sound very doable, plus I have to do something. Are you will to go back and forth via email? or Even a call/text, never spoken to a true Alaskan before :). From Chicago so I would be conscious of the time difference. Appreciate all the help I could get. Thanks Anthony FYI aleycock@hotmail.com
Update: a couple hours later, I reached out to B&S headquarters and after a more in depth search they found a drop in 19HP motor for $637, so I pulled the trigger and will be installing sometime in the next two weeks. HQ had a 3rd part distributor reach out to me with details. I will see if i can post details as well as you did in another tread. Appreciate your post, it put me in the right direction and gave me the comfort to attack this swap.
Sorry bud, Im a year late and a dollar short when it comes to replying :( My bad. I really thought I would get an email notice or something. Anyway, glad you were able to make the swap and good luck to you!
 
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