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1987 Evinrude 150 hp Broken crank

Cliff C

Cliff C

...
How often due yo u guys see a crank break off under the fly wheel on one of these motors?
and
How often do you see it while running?
 
I saw that happen just once in my time in trade, but that was to a 1964 40hp Johnson. It only happens while they're running, don't think they break off when sitting :) .

The breakage is due to an imperfection in the casting whereas a minor break exists in the casting, a case where metal does not attach to itself for some reason. Over the years, a imbalance takes place, a viberation which is perhaps not noticable, until the metal snaps completely at the flawed area. That's how it was explained to me many years ago, sounded logical to me.
 
It is a rare event that one of these cranks breaks-----------Manufacturing defect and perhaps a " fatigue " failure.---------How many hrs on the motor.---------------Breakage has nothing to do with removing the flywheel.
 
don't know sadly but its not likely to twist it off? also I hear this 4 or 5 times a year here and know i have one at home I cant believe the motor would be able to be held in place and produce enough force to brake it. but LOL
 
Over-Reving!

Boobie's post brings to mind a happening to me many years back. A close friend of mine (at least he was then), stopped over to my house with two salt water 150hp V6 engines (both in the early 1980s period) that he bought, both of which were good only for parts as singular engines. However, as a favor to him, I tore both engine completely down and built him one good V6 engine out of the two. You members who have done this know exactly what I went thru for him.

Finishing up, the engine was perfect in all respects. Whatever parts were imperfect on both engines were of course replaced with new components at cost, one of which was a flywheel which I let him have also at cost. I truthfully thought that he was going to use this engine on a boat for family use, however it came to light later on that he had installed it on some kind of hydroplane..... some kind of small racing boat.

A month or so later, he stopped by with the rig and said that he had a problem with the flywheel. Now, this is the standard 9-10-whatever amp V6 flywheel with metal magnets which are actually part of the flywheel, NOT the 35 amp epoxied on magnets. Impossible to damage, right? WRONG! This flywheel was actually damaged beyond belief.... outer portions of it were cracked, inner portions surrounding the magnets were split and cracked, the center taper was oblonged in areas, colors of blue and even red existed on the taper, etc. I was at a loss to explain how this could happen, so what was I to do? Install another flywheel and eat the monetary loss is what I did to keep a friend. However, he never once offered to cover any part of that loss, obviously and silently sure that the failure was my fault and that the loss should be fully mine.

Now, about a week later he stopped in again to let me know that the engine was once again performing perfectly. But thru the course of our conversation, he mentioned that the engine would no longer run at 10,000 rpms. It was all I could do to contain myself to keep from calling him every *&%#@#^ stupid *&$%#$!! a$$ name in the *&^%%$!%* book. However, this is when I explained to him that every engine has a top rated rpm, yours is 5500 rpm, and to exceed that is inviting the engine to explode, and obviously this is why your engine's flywheel resulted in being damaged. Still keeping my cool, but so cool that ice was dripping off my words. His reply..... Oh, I didn't know that, I guess I better change the propeller huh? Never a mention from him about the flywheel failure being his fault or any offer to cover the cost of it. He left, I haven't seen him since.
 
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Back in the early to mid 80s we'd see a broken V6 crossflow crank every once in a while. Word from the OMC engineers was that there was a harmonic imbalance at 6200 rpm. They told us to either go above 6200 or stay below it, just don't run at 6200 any longer than necessairy. Not saying we bought into that but it's just what they said.

We also saw some broken cranks when they were first starting to repair outboard cranks.
 
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