Thread: F100 - Ford Crankshaft journal bearings on Yamaha

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.