Broken Crankshaft on Kohler 25 HP on LT40 HYD

[Delawhere Jack]

It looks like it broke where the shaft diameter steps down just outside of the rear crank bearing. Could have been insufficient radius at the junction, leading to a stress riser. It looks like the crack developed over time. There is some corrosion in the crack around the outer edge.

Keith Fenner has done some excellent videos describing how and when cracks occur in marine shafting. Couldn't find the exact video, but lots of excellent content. https://www.youtube.com/user/KEF791

[Brucer]

I just replaced the 24hp Onan on my mill with a 25hp Kohler two years ago, and the alternator belt pulls in the same direction as the blade drive belt!

Interesting. Both my 2005 and 2006 mills, had the 28HP Kohler (EFI version of the 25 HP) and the alternator belt was opposite the drive belt.

For an air cooled engine 1000 hr is not to bad...

I've got close to 2600 on mine and my friend, John, has about 3000 on his. The first WM I ran had a 24 HP air-cooled Onan and it was up to 5200 hours when I last used it. The owner ran it for another year before it finally packed in -- around 5600 hours.

[paul case]

Chuck,
I believe his alt is on the opposite side. They changed it somewhere around 96?

PC

I just replaced the 24hp Onan on my mill with a 25hp Kohler two years ago, and the alternator belt pulls in the same direction as the blade drive belt!

Never did make sense to me, even changing the oil filter, I have to be careful not to spill into the alternator!

Yes sir, but that is on the mill, not the motor, and the newer ones are on the opposite side. You can see it in his pictures.

PC

[Chuck White]

You're right Paul, but I guess it is what it is!

Must be I was just overlooking it!

Might see about moving it sometime!

[paul case]

The statute of responsibility may have run out but someone should care enough to warranty that motor. Obvious everyone here it was not abuse that caused it. I know of an 97 LT40 w/onan 24 that the first motor went over 8000 hours and to only get 900 out of one just isnt right.
Pretty disappointing to me if they wont.
Glad you have a replacement on they way. WM replacement motors are pretty much plug and play. When I had to change one, it got to me quicker than we expected. Hopefully yours will too.

PC

[pineywoods]

You do have other options. When the briggs on my 95 lt40 got too tired to saw any more, I replaced it with a 25 hp kawasaki liquid cooled V twin. Pretty much a bolt-on swap. I did drill 4 new holes in the base plate and tweaked the belt guard a bit. Back up sawing  the same day. This is an industrial engine, should last a long time.

[drobertson]

glad you got another engine, I too would have went the Kawasaki direction rather than Kohler, of late in my opinion, very questionable changes to what use to be a workhorse engine design,

[UN Hooker]

HMMM, Maybe Kohler & Perkapillar are using Cast Iron crankshafts and not forged steel.  :-\     UN

[Larry]

I bet all small engines have cast iron cranks with the engineers realizing some will fail at a early age.  No sweat off their brow.  Its a cost thing.  A stand up company would make good on the repair as its a calculated risk on their part.

Now iffen you was racing your sawmill at Daytona I bet you could get a forged steel crank.

[Gary_C]

When I look at that broken shaft end, it does look like a classic fatigue failure as others have said. But I also have some concern with that outer band of material on the shaft which may indicate surface hardening which is not necessary or in any way desirable for pulley mounting on a shaft.

My other concern is the distance away from the engine bearing the pulley is mounted. Is there any way the pulley can be moved closer to the engine?