Gear Set Failure - Quality and Price Related?

[Gordon02]

He was running the boat in the 4,000 rpm range and it made a loud "Pop/clunk" in clean water. He shut if down immediately and used his tolling motor to get back to the dock. He asked me to have a look/listen so we put my OMC test wheel on it and backed it into my run tank - the noise was immediate and we shut it down.

The driveshaft was set to factory specification. As mentioned earlier, I purchased the factory gauge just for this shim/pinion set-up. The new gear used the same shim and bearing set-up. In the gearcase, there were no big chunks or teeth found - powder and finely ground pieces only.All bearings and all rollers are in-tact. This is the gearcase painted White alongside of my 1975 70's Gold one. Gordon

[Gordon02]

5 hours total. More than a dozen perfect trips fishing both river and lake spots. The 30 seconds was his estimate of how long it took him to shut it down after the noise.

[Fishinmymission]

If you can post more photos of the debris and gears(cleaned) I'll look at them. May or may not provide some more insight. If there are fracture surfaces fatigue or overload(i think i see fracture surfaces) there should be large chunks, if they did not exit through the seals then they have to be in the gearbox or oil somewhere. Also carefully inspect the propeller for any indications of a strike such as a submerged log, and all the bearings. It might even be worth it to cut open the forward gear bearing races to inspect for any evidence of heating, damage, or sources of drag that it could have placed on the forward gear.

[Fishinmymission]

You have two macro camera image comparisons of known metal overload examples of prop strikes and how it damages the forward gear. I can't tell from your pictures if you have the same type of fractures or not. Post better pictures and we might see a similar failure. Of course yours might have some additional smearing from running after the strike and when you tested it but one can easily tell the difference between smeared metal and fracture surface.
http://www.maxumownersclub.com/forum...rike-4131.html
https://www.lake-link.com/forums/boa...wer-unit-gears

[Fishinmymission]

I once pulled a manuever with a large heavy boat on a merc OEM standard fishing v6 gear case where I was trying to show off and I pulled a fast 100+ degree turn and in the turn I gave it full throttle and I though i heard a pop. 10 minutes of full throttle later i started hearing a pop synchronous with rpm every second or two. below a ceratin rpm maybe 2000 it would not pop though. I took apart the gearcase and found enough(maybe 1 or two full two or three partial) missing teeth on the pinion and forward gear to conclude that only with a certain load and alignment between the damaged teeth would cause what i thought was a slip across the forward gear. The clunk would be it remeshing after skipping. At low rpms and load the mesh accross multiple teeth and the momentum of the parts must have prevented skipping. The water moving sideways across the prop when i pulled the maneuver while slamming the throttle must have created some strange high load that did the damage.

[Capt.Insane-o]

The 5 hr run time is an anomaly..gross improper set up will appear immediately...butt hay..there is no signed work order in front of me...*shrug*

[flabum1017]

The 5 hr run time is an anomaly..gross improper set up will appear immediately...butt hay..there is no signed work order in front of me...*shrug*

But..... how much of that 5 hours was at WOT?


These were not OEM gears. Probably Chinese knock-offs and with the tarriffs, probably even lower quality. Shimming cheap gears does not guarranty a good build with badly made parts. He could have hit a minnow or a log.... could have been shimmed wrong, could have used the wrong gear oil..... could have dropped a pinion bearing, could have had residual debris in the housing..... even the hub failed and shoved the prop into the housing.....

To me, looks like a strike, mud, sand, log....... to get a few teeth scrubbed off and the pinion still in mostly one piece (not exploded).

[Fishinmymission]

The 5 hr run time is an anomaly..gross improper set up will appear immediately...butt hay..there is no signed work order in front of me...*shrug*

I respect your wisdom captain insano but I disagree here. If the issue is fatigue or wear or bearing related it could take 5 hours for the bearing to seize, a fatigue crack to propagate through a tooth, or wear to creat an alignment issue. I have personally worked many jobs on aircrafts that we attributed to bearings failing a few to many hours after installation due to too high a preload or too lose causing them to run outside the designed load path or with too much interference etc.
Also possible not oem quality but can't assume without testing the material. It could be high quality alternative.
Can't be certain but I'm leaning towards either a log or ground strike, or forward bearing failure. The metal holds the evidence either way if examined properly.

[Captaincj]

But..... how much of that 5 hours was at WOT?


These were not OEM gears. Probably Chinese knock-offs and with the tarriffs, probably even lower quality. Shimming cheap gears does not guarranty a good build with badly made parts. He could have hit a minnow or a log.... could have been shimmed wrong, could have used the wrong gear oil..... could have dropped a pinion bearing, could have had residual debris in the housing..... even the hub failed and shoved the prop into the housing.....

To me, looks like a strike, mud, sand, log....... to get a few teeth scrubbed off and the pinion still in mostly one piece (not exploded).

What's the "wrong" gear oil?

[Capt.Insane-o]

What's the "wrong" gear oil?

Lets not go there lol...i will have to remember to not hit any minnows or run wide open this weekend Being there is not a lot of shimming options in an omc case I would box those gears up and return them to the manufacturer and next time check the backlash after assembly.

[Captaincj]

Is this another one if those transom saver, start in gear, best oil questions?

[flabum1017]

What's the "wrong" gear oil?

Using Mercury oil in an omc

[Gordon02]

Guys, the bearings are all brand new and still look/turn great - even covered in metal "coffee grounds". I took this set to my long-time friend, outboard marine mechanic, former boat dealership owner, and former Mercury certified technical instructor today. He looked and said that he had never seen gear teeth pulled apart like these are - not simply broken, chipped, or stripped. The base of the teeth look like smeared "peanut butter" consistency - like a galvanized water pipe would look if hammered/chiseled. He also believes these were improperly hardened.

Theses came from that eBay seller linked in the 3rd post. Their listing says "Made in USA" at their Wisconsin facility, but they quickly told me yesterday that 90 Days is it for warranty. For the record, this boat was in deep, clear water that he runs all the time and no tree, stump, or sandbar was hit. 99% of his running is 1/2 to 2/3 throttle. In fact, on this day, he had his 4 year old son with him and was taking it easy.

Thanks for all the inputs. Bottom line - I will not be buying from this seller again and will not buy aftermarket gear sets unless they are reputable.

Gordon.......here is that link

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

[Gordon02]

Well, there you go.....I'm guilty. I broke it! I filled it with my Mercury Performance + Gear Lube that I use in my Merc SS/Sportmaster.

Gordon

[Dave S]

Best use used.... they have a proven pattern and past......what is the problem? just find a used case and GO......gotta be a load of used......in your area... if not ya didn't look.