Johnson 35HP Magneto Explodes!?!?

M

mnsherick

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Dec 3, 2009
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So after nearly a year of use since my last repair (thanks iBoat brothers) I've had yet another failure and had to be towed back to the dock.


Oct. 23rd 2010

Motor ran great this day no problems what so ever.

My transom saver broke and my motor dropped during transport on the way home from the lake.

Oct. 30th 2010

Motor was harder to start than normal but it was slightly cooler than the previous weekend. Got her warmed up and she seemed to run fine until I got to my stopping point and wanted to idle down, at this point when I moved the throttle position to "idle" the motor would die. When I would start it back up I had to run at 50% throttle or higher to keep it running, also the throttle handle kept "pulling back" like it was spring-loaded instead of keeping it's position that I placed it in.

On the trip back it broke down, upon inspection the first thing I noticed was a powder or 'dust' all over inside the motor cover on the engine block/air filter/ and case. Also small 'chips or chunks' of a metal-plastic material almost looks like chipped up pieces of stone not magnetic from what I can tell.

At this point I don't know where to start, engine cranks but doesn't cough or anything else that would indicate a start. Also no spark, sooo... magento explosion???

-Matt
 
F

F_R

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Re: Johnson 35HP Magneto Explodes!?!?

Never heard of such a thing. You have a 1978 with CD ignition. Why don't you identify what happened and report back?
 
M

mnsherick

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Re: Johnson 35HP Magneto Explodes!?!?

F_R said:
Never heard of such a thing. You have a 1978 with CD ignition. Why don't you identify what happened and report back?
Click to expand...

Waiting on a service manual so I can start tearing it down. I don't know where to start, and my biggest concern with removing the fly wheel is having the timing go out.

After I make some progess on it I'll report back.

-Matt
 
kfa4303

kfa4303

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Re: Johnson 35HP Magneto Explodes!?!?

Could magneto "explosion" = Blown Coil(s) ?

Maybe bad idle etc..... b/c running on only one cylinder due to blown coil? Just a gues. Good luck getting her runnig again. You're in the right place.
 
B

boobie

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Re: Johnson 35HP Magneto Explodes!?!?

Get the flywheel pulled off and inspect. Possible a screw loosened up under the flywheel.
 
F

F_R

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Re: Johnson 35HP Magneto Explodes!?!?

mnsherick said:
Waiting on a service manual so I can start tearing it down. I don't know where to start, and my biggest concern with removing the fly wheel is having the timing go out.

After I make some progess on it I'll report back.

-Matt
Click to expand...

Removing the flywheel will not affect the timing. But be sure you do it according to the book, with the right tools. Countless motors have been destroyed by failing to do it correctly.
 
kfa4303

kfa4303

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Re: Johnson 35HP Magneto Explodes!?!?

F R is right. The right tools are essential. I've had good luck renting/borrowing them from auto parts stores like Auto Zone, O'Reilly's. They ususally just ask you to put down a deposit for 24-48hrs then credit the deposit back to your credit card when you return the item. You'll need a flywheel (a.k.a. hamonic balancer) puller with GRADE 8 bolts which probably will not come with the puller, but I was able to get 2 pair at Lowes for like $4 total. You'll probably also need a torque wrench so you can tighten the flywheel nut back down to the porper spec. Otherwise, most of the other tools are stuff most folks have in a basic tool box. Good luck!
 
M

mnsherick

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Re: Johnson 35HP Magneto Explodes!?!?

kfa4303 said:
F R is right. The right tools are essential. I've had good luck renting/borrowing them from auto parts stores like Auto Zone, O'Reilly's. They ususally just ask you to put down a deposit for 24-48hrs then credit the deposit back to your credit card when you return the item. You'll need a flywheel (a.k.a. hamonic balancer) puller with GRADE 8 bolts which probably will not come with the puller, but I was able to get 2 pair at Lowes for like $4 total. You'll probably also need a torque wrench so you can tighten the flywheel nut back down to the porper spec. Otherwise, most of the other tools are stuff most folks have in a basic tool box. Good luck!
Click to expand...

10-4 I already picked up the puller from my shop today, I had 2 grade 8 1/4-20 bolts that fit, but I need to get 3 the same to pull it. Also grabbed the torque wrench as I knew I would need it.

How do you keep the flywheel from turning while loosening the nut on top? I have the socket it's a 1 1/16" but I have no way to keep it from turning and don't want to break anything.

Another update...

I checked the terminals at the coils and I get 12volts at the red terminal, and nothing at the other 3 yellows that are going to the coil packs. It looks like the wires are coming from up under the fly wheel, that's why I'm headed that direction with the diagnosis.

more later.

-Matt
 
F

F_R

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Re: Johnson 35HP Magneto Explodes!?!?

12V at red and zero at the yellows is right. The rectifier prevents backflow to the yellows. Those wires are for the battery charging function, nothing to do with the ignition function. But nevertheless, it is all under the flywheel.


EDIT: at the risk of sounding like a broken record, the correct tools make it easy. A strap wrench is the correct tool for holding the flywheel. But for this one, you can get creative.
 
Dexta

Dexta

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Re: Johnson 35HP Magneto Explodes!?!?

I've heard of guys putting soft rope down the spark plug hole to stop the wheel from turning. Any comments?
 
F

F_R

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Re: Johnson 35HP Magneto Explodes!?!?

Whatever floats your boat.
 
kfa4303

kfa4303

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Re: Johnson 35HP Magneto Explodes!?!?

I've seen and heard of folks doing the same thing, but it just doesn't seem wise to stuff stuff into perfectly good cylinders :/ They do make special tools to hold the flywheel, but I try not to buy one use tools if I can help it. I was having trouble with the same issue on a 33hp and started a thread here about it, but eventually I used a long nylon strap with an S hook on one. It's actually just a 10- 12 ft nyon strap from a ratchet strap set I use to strap my canoe into my truck. I just wrapped it around the flywheel several times and hooked the s hook which comes sewn into one end of the strap, on to the lifting eye on the engine and it works great. Essentially, the nylon strap acts as a giant strap wrench. Be sure you wrap the strap in the proper direction so that as you tighten/loosen the flywheel nut the starp will tighten around the flywheel so that the harder you loosen/tighten the nut, the harder the strap tightens. I hope that helps some. Just a suggestion, but it really works great for me. Good luck.
 
M

mnsherick

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Re: Johnson 35HP Magneto Explodes!?!?

thanks, I'm going to try and get that fly wheel off this week or next. Work has been crazy!!

-Matt
 
royal0014

royal0014

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Re: Johnson 35HP Magneto Explodes!?!?

What kfa4303 said ^^^
Did the same thing, worked like a charm. Reversed the set-up to put the flywheel back on ;)


<<)))(((>>
 
M

mnsherick

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Re: Johnson 35HP Magneto Explodes!?!?

UPDATE!!!

After the thanksgiving holiday and getting the christmas lights put up, I finally found some free time, and the help of my grandpa and my dad to get that thing tore apart.

Looks like my assumption was correct. Stator has came apart...

It seems the power pack assembly plate (has 4 screws holding it on) the screws backed out and allowed enough play in it to tear up the Stator against the bottom of the flywheel.

Off to find a stator on the web, any suggestions?




See pics below.
IMG_0922.jpg


IMG_0923.jpg


IMG_0924.jpg
 
M

mnsherick

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Dec 3, 2009
Messages
25
Re: Johnson 35HP Magneto Explodes!?!?

I got a used stator on ebay, it arrived today and I got it all put back together in about 35 mins. First start it fired right up! Engine sounds great, I'm going to take it out next week some time and give it a run just to make sure it's in good working condition before the 2nd season opens up.

The repair manual I ordered from the library never came in, does anyone know what the torque spec is on the flywheel??

thanks

-Matt
 
B

Big Rush

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Oct 4, 2010
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Re: Johnson 35HP Magneto Explodes!?!?

My book shows 100 to 105 ft/lbs, but I dont know your exact motor.
I use a couple of large lead sinkers on each side of the flywheel gear to hold it in place while I break the nut loose. I dont know if this is a good idea, but it has worked for me. Ruins the sinkers though.
 
samo_ott

samo_ott

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Re: Johnson 35HP Magneto Explodes!?!?

If I can ask how much was the stator on Ebay?
 
Joe Reeves

Joe Reeves

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Re: Johnson 35HP Magneto Explodes!?!?

Hopefully you used Loc-Tite on those stator retaining screws.
 
1946Zephyr

1946Zephyr

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Re: Johnson 35HP Magneto Explodes!?!?

Holy toledo, what made that one come apart like that??:eek:

Joe, you sure you want to use lock tite on those screws? what if it needs to be replaced again down the road? I would think proper torque would be efficient, as well as good lock washers.:cool:
 
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