Gear Set Failure - Quality and Price Related?

[Gordon02]

Guys, I have built and set-up several gearcases over the years and have always paid close attention to the factory manual and shim specifications. This 1989 120 Evinrude V4 looper is no exception. I followed the manual - even purchasing the special OMC driveshaft shim/bearing set-up spacing tool.

This is my first time that a "gear set" grenaded on me. This was a brand-new 3-piece matched gearset purchased on eBay for 1/3 the cost of OMC (BRP) sets. The seller had a good rating, but these failed teeth looked stretched and almost pulled sideways. I personally have not seen teeth pulled/stretched like this before and think that this set was not hardened properly.

I'm posting these hoping for opinions and input on the failure. This is a close friend of mine's outboard and he'll foot the bill, but I don't want him wasting more money on cheap gears that will not hold up. This has less than 5 hours on it.

Thanks, Gordon

[MattGreen]

What brand were the gears ?

mattt

[Gordon02]

These do not have any markings on the gears themselves. They were sold by an eBay seller "GearPros" based in New Richmond, Wisconsin.

Here is a link....

https://www.ebay.com/str/gearprosmfgandmore

[Chaz]

Guys, I have built and set-up several gearcases over the years and have always paid close attention to the factory manual and shim specifications. This 1989 120 Evinrude V4 looper is no exception. I followed the manual - even purchasing the special OMC driveshaft shim/bearing set-up spacing tool.

This is my first time that a "gear set" grenaded on me. This was a brand-new 3-piece matched gearset purchased on eBay for 1/3 the cost of OMC (BRP) sets. The seller had a good rating, but these failed teeth looked stretched and almost pulled sideways. I personally have not seen teeth pulled/stretched like this before and think that this set was not hardened properly.

I'm posting these hoping for opinions and input on the failure.

It's hard to tell when you show real close up shots of "nothing left". However in the one picture that does show a bit of "pattern" there are a few tell tale signs. I'm sure you don't want to hear it, maybe you can show a few better pictures, maybe the Captain will join in ..

The pinion gear looks like it was way shallow.
The forward /reverse or both looks like they were set tight up against the pinion with no lash and was chewing at the outside of the root on both the drive and coast side of the remaining teeth. You asked ..

[Gordon02]

Thanks for the input. I do want to figure this out before building it a 2nd time. The reverse gear is perfect - not a single nick, chip, or burr.

Another odd fact is that not a single tooth was found. Only small chips and chunks - nothing larger than the head of a match tip was in the entire gearcase. Not only were the teeth sheared off, they were finely ground - all within 30 seconds of running - not like anything I've seen with hardened gears. Gordon

[wolfgangb]

You are not alone. Recently opened a new Sportmaster which after 3 hrs of (competition) running lost a pinion tooth. The shambles inside the gear box jammed the driveshaft, to the extent that the top splines were bent. Driver was lucky - switched off just early enough. IMO too tightly set at the factory. I prefer to set the backlash right at the maximum of the spec, to maintain sufficient lube gap. Very essential to replace all bearings and clean casing before rebuild - especially on floating prop shaft gearboxes, like Fleetmaster and Torquemaster. Wolfgang (South Africa).

[Chaz]

The reverse gear is all you gave us to go by. It shouldn't have a "Hi-mileage" wear pattern already embedded ( could be lighting and old azz eyes ) ( again more pit-cherz ) down @ the root of the teeth unless it was in a bind ( no lash ) .

I have broken stock planetary gear sets in Powerglides and 9" Ford street gears. They make them extremely hard with the thought that they will last forever. But when a tooth breaks, it shatters like glass and sets off a chain reaction that leaves nothing but little pieces.
An old guy (gotta love em) taught me that I could take them to a place called "air burners" and they could bring them up to 500* overnight and it would soften them up a bit. It's true, they would wear rather than fracture. Eventually I had to just spend the money on good hi-nickel parts.
If you didn't find any "very sharp splinters" of teeth, then chances are good that the gears are powdered metal. These days lots of parts are made from powder. I haven't really followed that technology, but if these kids today can take a junkyard 5.3 LS with powder rods in it, put a hair drier on it and make 800 - 900 HP then it can't be too hateful.

[BOATMANBLUES]

if the previous gear set broke , or if anything got chewed up in it then you need to check the case where the forward thrust washer rides...the shrapnel stipples this surface and jams the fwd gear back into the pinion...you can still get your .020 clearance by shimming up the upper bearing,but the teeth are riding too high on the gearset and will strip the teeth right off..

[Dave S]

Thats just a V4 looper..... just too many HPs.....Strange that the pinion gear is not shaved....still has some teeth.

[Fishinmymission]

Clean the oil and debris, take many more photos at many more angles, get the story as detailed as possible from your friend what the symptoms where of the gear case up to and leading to the failure of that gear case. I do failure analysis for pinion and ring gears all the time for my job, but having the parts in your own hands with a 50x microscope makes the job 95% easier than off of someone elses camera photos. And then on the other jobs having a SEM is extremely helpful. Basically you are looking for the origin and what modes of failure occurred in the metal. Fracture surfaces that have not been rubbed over by sliding metal will show if the material cracked and propagated with load cycles in fatigue or if they were sheared off at once in overload. Gotta piece together the story of what happened first and what is secondary damage. The first teeth to be loaded in the sequentially damaged teeth might have some clues or the surfaces could be destroyed to the point that camera photos don't show ****. If I had a lab Id also get to make cross sections and perform microhardness surveys traveling inwards from the flanks to make sure the carburizing created the correct hardness at the correct depths but thats not something you'll be able to do. Of course we also check the elemental make up and microstructure and dimensions but once again out of the question here.
You really cant assume it is or isn't bad material till you have it tested. Is only one half of the forward gear not hardened correctly? very unlikely but possible it was partially masked during carburization, not quenched, or heat damaged causing it to soften. You also wont be able to tell if they are using the same type of steel and forged manufacturing and cutting operations that the OEM would use. Most likely some high load or fatigue crack started on one tooth and then once that tooth was gone or deformed it created high loads or possible skipped and slammed into the next tooth until that one was gone and so on. This may or may not have been due to inferior materials or manufacturing. If you see fracture surfaces from fatigue or overload you should find large chips though. Or it all happened at once and it wiped out the 8 plus teeth from some load instantly being created(bearing seizure from debris, or bearing defect, or propeller strike). If this was the case those teeth would be found somewhere. I'm 75% sure i see some type of fracture surface from the oily photo which means large chunks of teeth should have gone somewhere.

[vnemous]

Probably nothing to do with your assembly but no magnets picking up loose bearings.

[flabum1017]

Probably nothing to do with your assembly but no magnets picking up loose bearings.

Easy to drop a pinion bearing roller and miss it....

[Capt.Insane-o]

The forward gear looks mismatched to the set...anyhoo it ate itself alive.

[Gordon02]

Guys, I spent months restoring this Norris Craft and 120 Evinrude while showing my good friend and neighbor how to work fiberglass and epoxy laminate. We rebuilt the transom and rear bilge area (shown). Previous owners had drilled several holes for different mountings of transducers over several years. Those holes were poorly sealed and the bilge area was wet and water-logged. We removed all of the sides, flooring, and foam until every damaged/wet component was gone. All supports, flooring, tank supports, and flotation boxes were made using 100% hand-laid composite.

No shortcuts were taken. The 120 Evinrude was taken apart for painting only. I did have to take the gearcase apart to find out why it would not stay in reverse. We went though the factory set-up for throttle and shift linkage twice, but it would "pop" out of gear after only a few seconds of running. It was then that I saw damage to the shift dogs on both forward and even worse on the reverse - that prompted the need for a new "set" of 3 and a brand new OMC shift dog.

[Capt.Insane-o]

So it has which? close to five hours or less than 30 seconds of run time before it shredded?