Yes, broken crankshaft. Now what? (was "Busted crankshaft?")

[Rick Stephens]

Do i need to find another exhaust manifold if mine is cracked? I should be able to just change the down pipes correct? Or can i put mine on and wait and see if it's still good? Can i test it somehow? Thanks

You can test it using acetone. Lots of tips on doing that. Basically, acetone will flow through a crack without heat or pressure where water won't.. If you have a cracked manifold it usually needs replacing. Might be possible to epoxy a crack depending on where it is.

 

[achris]

Will all the race boats, race cars,and street cars I have never seen that. Ive seen flywheels just explode into shrapnel but it was contained in an explosion proof bell housing.. The only broken crankshaft I have seen was on a Black Max that hit a boulder near Staten Island, NJ.Here`s the prop shaft from it....

The very first engine I had to repair when I bought my boat shop in 1995 was in a Western Australian Fisheries patrol vessel. Engine was a 454 with a Bravo behind it. Broken crankshaft between the cylinders 2 and 3.... The only explanation Mercury could come up with was that an extra pulley mounted on the crankshaft for a 'pot winch' pump had put too much load on it. We all thought it was hogwash at the time (as the previous engine had been in the boat for 4 years with the same pulley and never had a problem), and nothing I have seen in the interim 20+ years has convinced me otherwise. The weight of opinion was that the crank was flawed from the factory.... We couldn't do tests on it as Merc claimed it under the warranty.... So we'll never know....

Chris............

 

[achris]

Do i need to find another exhaust manifold if mine is cracked? I should be able to just change the down pipes correct? Or can i put mine on and wait and see if it's still good? Can i test it somehow? Thanks

Cracked internally, replace it (or you'll be replacing another engine very soon)... Cracked externally only, you may get away with gouging out the crack (drill 1/16" relief holes at each end of the crack) and filling it with some form of epoxy. I have had very good success with 'cold welding' cast iron, but it is VERY time consuming and requires a deft hand....

Chris......

 

[superfets]

The very first engine I had to repair when I bought my boat shop in 1995 was in a Western Australian Fisheries patrol vessel. Engine was a 454 with a Bravo behind it. Broken crankshaft between the cylinders 2 and 3.... The only explanation Mercury could come up with was that an extra pulley mounted on the crankshaft for a 'pot winch' pump had put too much load on it. We all thought it was hogwash at the time (as the previous engine had been in the boat for 4 years with the same pulley and never had a problem), and nothing I have seen in the interim 20+ years has convinced me otherwise. The weight of opinion was that the crank was flawed from the factory.... We couldn't do tests on it as Merc claimed it under the warranty.... So we'll never know....

Chris............

Ya. A defect would be most likely.

 

[superfets]

Cracked internally, replace it (or you'll be replacing another engine very soon)... Cracked externally only, you may get away with gouging out the crack (drill 1/16" relief holes at each end of the crack) and filling it with some form of epoxy. I have had very good success with 'cold welding' cast iron, but it is VERY time consuming and requires a deft hand....

Chris......

Will my exhaust elbow fit in the older engine with the older style exhaust manifold?

 

[achris]

Will my exhaust elbow fit in the older engine with the older style exhaust manifold?

The gasket is the same from 1968 to present, so the bolt pattern is the same. So in theory your elbow will bolt up to it....

Chris.........

 

[superfets]

The gasket is the same from 1968 to present, so the bolt pattern is the same. So in theory your elbow will bolt up to it....

Chris.........

Finally some good news! Thanks. :eagerness:

 

[superfets]

No Title

update: I think i figured out how the crankshaft broke the way it did. I had a chance to have a closer look and think about it a bit. I figure the boat was sitting on the trailer with the nose up. Way up. Then in rained, snowed, melted, and froze. With either the plug in or a plastic bag in the bilge plugging the drain. And it looks like water was about 1/3 up the flywheel. See attached pictures. And when it froze it pushed the flywheel and the block apart and that's how it broke. Mystery solved. So we all learned something today. Thanks for all your help. Now join me on the next step and getting this boat running with a newish engine in the new thread. [h=1]"Swaping out 3.0 L engines, what to think about."[/h] P.S. I'm going to pull that crankshaft and try to weld it back together. Ya gonna try it. But that's going to be a new adventure for next winter.

 

[Bondo]

P.S. I'm going to pull that crankshaft and try to weld it back together. Ya gonna try it. But that's going to be a new adventure for next winter.

Ayuh,..... Unless yer lookin' for a guarantied failure, toss it in the scrap bin, or make an art piece outa it,....

 

[superfets]

Ayuh,..... Unless yer lookin' for a guarantied failure, toss it in the scrap bin, or make an art piece outa it,....

Lol. I know your right.

 

[alldodge]

Welding a crankshaft back together is one of those "hold my beer and watch this". I'm sure it can be welded back together, but getting it balanced so the vibration won't tear it self apart is another

 

[Grub54891]

I saw the damage a loose flywheel can do. A guy revved to his car for laying rubber, The flywheel removed itself from the vehicle, and proceeded to tear up the blacktop, hit the curb, took a chunk out of the curb, flew up through a shop window and destroyed a bunch of merchandise. On a boat it would sink ya real quick!