Thread: F100 - Ford Crankshaft journal bearings on Yamaha

Originally Posted by Slab

And here's one of the bearings up close. You can see that only the center has the scratches. The sides don't even show any wear. And that's more or less how they all look.

You can see debris was impacted in the softer bearing material. This material is what damaged the Journals IMO. Still we may never figure out what practices were carried out wrong but now we know the Block is full of this material and needs pressure washing to remove all the contaminants possible. Yamaha 4 Stroke Outboards are the most sensitive to clearances of all the engines I have read about. Since I only Build 2 Stroke Outboards and Hot Rod Engines I have no direct experience with 4 Stroke Outboard internal engineering. Yamaha tolerances are extremely demanding unlike automobile engines so very strict adherence to clearance protocols is necessary or this repair will be short lived IMO.

Originally Posted by Rojo

You can see debris was impacted in the softer bearing material. This material is what damaged the Journals IMO. Still we may never figure out what practices were carried out wrong but now we know the Block is full of this material and needs pressure washing to remove all the contaminants possible. Yamaha 4 Stroke Outboards are the most sensitive to clearances of all the engines I have read about. Since I only Build 2 Stroke Outboards and Hot Rod Engines I have no direct experience with 4 Stroke Outboard internal engineering. Yamaha tolerances are extremely demanding unlike automobile engines so very strict adherence to clearance protocols is necessary or this repair will be short lived IMO.

Great info, and I agree. What I just don't get is, the first place the oil goes from the oil pump is through the oil filter. And then it goes to the crank journals. At least that's what I see when I look at this engine, don't really know 100%.

Anyway, ain't that oil supposed to be clean, it shouldn't have debris. So where's that there debreee come from. Is it being pushed through the bypass valve of the oil filter on a cold engine (cause the earl is too thick still). Those large scratches can't be coming from microscopic particles that might make it through the filter, can it? What's the science! A guy gotta know!

"very strict adherence to clearance protocols " so you're saying I have to use a specific thickness duct tape to perform this repair! hmm, may be out of my wheel house. I guess we will see if'n I can pull this one off. Actually, thanks for your advice John. Cause sometimes I don't even use torque wrenches. I'll have to find mine now! Seriously, I rarely use a torque wrench as I've seen some of those torque specs are way too low, IMHO! I like the guten-tite method. I guess I'll have to use the book specs on this one.

Originally Posted by Slab

My latest expert diagnosis as a certified YouTube watcher extraordinaire! I actually emailed this video to the guy from Mahle in the video above. Lets see if I get a response.

I GOTS A RESPONSE FROM Mahle's Dan Begle, yay. Great company.


Ed,

I would agree with you on debris damage. Considering the length of service, this could have been some contamination on the build. You said it correctly when you noticed the debris coming mainly from the upper oil groove which makes a heavier debris path on the lower main.

Dan Begle
MAHLE Aftermarket Inc
Technical Sales Engineer

So I had to ask Dan another question: Dan, I just have to ask, how can all this damage happen so fast to these bearings when the oil passes through an oil filter directly before going to these bearings? It's like it was run without an oil filter.


Ed,

That is a great question. Typically the contamination is inside the engine such as honing grit, airborne debris, grinding dust, etc. I am not sure what filter is on this application but for the sake of this conversation, it realistic has a higher micron rating of filtration than what film thickness is between the crankshaft and the bearing. A given filter may have a micron rating of 40 microns. That means it only captures a percentage of the 40 plus microns of debris. 40 microns is .0016”. Typically the oil film thickness is considerably less than that. So even with a filter properly doing its job, the particle size will embed into the bearing and cause a disruption of the film thickness. I presented on this at the EPIC tech day at PRI recently. It wasn’t exactly on filtration but that 45% of bearing failures are from debris.

Hope this helps!

Dan Begle
MAHLE Aftermarket Inc
Technical Sales Engineer

That is a great explanation. Certainly makes sense to me

I usually don't back up from much but my Buddy in Houma gets premium $$$ for building Yamaha 4 Strokes. He's the only local I know capable of building reliable Yamaha 4 Strokes. After reading all involved to rebuild a F250 Yamaha I Punted to another team.

Originally Posted by Rojo

I usually don't back up from much but my Buddy in Houma gets premium $$$ for building Yamaha 4 Strokes. He's the only local I know capable of building reliable Yamaha 4 Strokes. After reading all involved to rebuild a F250 Yamaha I Punted to another team.

Well that’s not what I wanna hear! Geez, you gonna scare me off this rebuild! NOT! What do I got to loose but a little money and maybe some pride too! And what do I got to gain, pretty much the same thing. So challenge accepted!!!!


Sent from my iPhone using Crappie.com Fishing mobile app

Go for it Boss. A man learns by doing. Heck I have already learned alot from you doing. That last message about particles in the oil contaminating the bearings makes perfect sense once one is made to think about it. Knowledge is power.