MF165 gas G176 Crank - replacing connecting rod bearings

I have a MF165 gas with G176 engine. I was loosing oil pressure and thought it was the oil pump. but thanks to the great help here, it looks like the connection rod bearings are worn. the first 2 from the front have a little play, maybe 1/32. the 3rd is tight, the 4th is where the bigger problem is. have about 1/16 in. play and this is where I think the slight knock is coming from. I have a couple of questions. 1- can I just replace the connecting bearings? reason, I need the tractor back asap and don't have time to split the tractor to take the crank out and re-ground/replaced. so if I can just replace bearing while in tractor, that would be great. the 2nd question is when I disconnected the 4th rod and looked at the bearing, it is little warn. but I noticed that on the crank where the bearing was, there are "micro" groves - like record groves. is that correct? from what I can tell, they look like there were put there as the are evenly spaced (like a record). the bearing I took off was marked .010 so can I just replace with a new over-sized bearing of .010? everything else looks fine and no ware. thanks for all the help!
 
Good morning:

At the end of the day you shall make the decision $$$$$$$$$.
I have never changed Bearing inserts / Shells without first using a MICROMETER to check the Diameter of the Journals. The Journals could very well be Tapered and or, OUT OF ROUND. There is the likely hood, that if the engine ran under load with minimal oil pressure, the crank MAY have to be ground.
The best with your decision:

Bob....40 + years Licensed and experience Journeyman with Power Engineering Certification:
 
thanks Bob for the insight. not of course what I was hoping for. are the groves normal? and if not out of round, can I use new bearings for now to "patch" it until I can break it down this winter to put a new crank and bearings? I use it mostly for mowing with a 6 foot finishing mower, moving dirt and the loader on 4.5 acres. only about a couple of times a month if that.
 
Take a look at the back side of the bearing inserts,verify if and how many journals have been turned Undersize? Not everyone has the $$$$$$$$ to turn all Journals undersize. Not all Journals require to be turned undersize always. However,90% +,when one Journal requires turning the rest shall also require turning.
Given that someone has been working on this Engine,there may have been an oversight with FOREIGN material left In some part of the OIL Gallery,thus the " phonographic" finish on the Journal. There may have been foreign material pass through the Oil pump and the Main engine Oil filtration system.
Consider checking the Crankshaft THRUST. Excessive thrust Clearance has and could contribute to low oil pressure causing Journal bearings to fail.
Consider removing the Main Bearing Caps and verify the running clearances with Plastiqaue. The CONNECTING ROD bearings on most engines receive their oil from the Main Bearing oil supply.
Bearing clearances on a Crankshaft Journal are usually referred to in ".000" (thousands of an inch)e.g..002 .003 .002>.0035 Etc,etc,)
Check with a service manual specific for your engine as to the CLEARANCE allowed between the Crankshaft Journals and the bearing insert.. Then use plastiqauge to verify the clearance between the Crankshaft journals and the new bearing inserts.
Lastly, I would and have always used a MICROMETER to verify the Diameter and condition of the crankshaft Journals.
The oil pump is the heart of the oil system. Possibly other shall have their point of view as to how to check the oil pump or replace it? At least check to verify that the ROTATING COMPONENTS are all KEYD to their respectful shafts and turn.

Bob...
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