Broken HP 500 Crank
 

This crank is out of a Merc HP500 that has about 150-175 Hours and No blowers on this motor. Has anybody else broke a crank like this ??? It is a pleasure boat not a race boat.

I've never seen one broken like that before. I've seen 302 cranks broken at the front journal due to Ford's lightweight crank design.

Being the break is on the counterweight and seing that it is a jagged break, I would say that it was an imperfection in the steel. A crank that breaks due to stress will break at a stress plane and in a more or less clean break. That looks like just a bad crank from the factory.

Tyler,I was at baker engineering 7 or 8 years ago chassis dynoing a circle track car and they had about 8 or 10 broken bbc cranks sitting in the corner similar to that,when I asked what the hell they were out of the Jack said they were all gm factory steel cranks out of boats. They were broken in various positions next to rod journals where the crank pin attached to the counterweight similar to what you have,Smitty

What kind of damage did the frt main brg show??

I have. Broke a GM steel crank in a slightly built up 454. Didn't look too much different than that.

Me too. The funny thing is it still ran, just knocked like a *****.

Just an observation, but is it possible the oil passsage being so close to the outer edge be a cause? Seems like it should pass more through the center of the casting.

Mine didn't run. When I tried to restart the engine sounded funny & when I checked it the front pulley wasn't turning. I knew it was over, time to idle home on the other one.

It has to be defective ,because mine hasn't left the building yet at 860hp:eek: tic tock:rolleyes:

Back at the the marina my old boss broke one on a worked over 502' Mag that was making about 600 hp.

He was running about 5600 WFO when it happened, they said it was the worst sound they ever heard but the motor did keep running with a loud knock.... :D

My buddy had a stock Merc 500 efi w/ 150 easy hours and had the same thing happen. It looked identical to your pic.

Callies Crank
 

Tyler, very similar, snap, crackle, pop, to my 558 with a Callies Crank

160 hrs on hp500 with whipple, same thing, ran, horrific noise, when I went through the engine the pistons showed signs of detonation so I figured that was the culprit

She's a strong running 540 now, in my Pantera which needs a good home:drink:

Maybe this guy could tell you:evilb: :evilb:
http://www.goahead.org/

Tyler:

Lets face it, GM cranks ain't no perfect parts. I suspect with mass manufacturing and the "bean counters" involved its easier to slip a few through.

Sounds like its going to be a nice nrew motor job for you.

Regards,
Ray @ Raylar

I wonder if that crank would have passed a magnaflux or zyglow test prior to the breakage?

GM crank....nuff said.:(

[QUOTE=mrhorsepower1;2085194]I have seen them break like that in a Drag Race app. The crank had approx. 2000 passes and the engine was making about 875 HP. Broke in the same area. Never seen it in a low horsepower engine though. Ouch! Looks like it's time for a 4.250 stroke !

I Broak One In The Same Spot, Same Motor. Didn't Loose Block. New Bearing Cap And Line Bore And It Was Fine. I Have A 500 Crank If You Need One.
Ron Bender 216-390-1330