MR1 low oil pressure

[Neutron]

So I’ve been in the process of rebuilding the 2 vx110 engines out of my ar210. Reading the service manual it says the main oil bearing clearances are .0002” - .0012” normally speaking. the crank mains measured around 1.3381. Typical rule of thumb on bearing clearances is usually .0010” for every inch of journal diam. which should be around .0013”. Because I was skeptical about having such tight clearances, I called SBT and asked a tech what they do on their rebuild. They told me they go with the largest bearing size I think they told me green. He said the bearing clearance should only matter at an idle and when warmed up on RPM it wouldn’t matter. My guess is they don’t follow the service manual specs rebuilding these engines and putting larger bearings in the engines which creates lower oil pressure. Hopefully this weekend if we don’t get rained out I’ll be able to install both engines back in the boat and verify I have good oil pressure

What was your end result measurement.
I would not listen to SBT and go by the factory specs

 

[Nikokrzynowek]

so the plastigauge only went down to .001” so I ended up buying a mitutoyo dial bore gauge. Here’s what I got for measurements
Starboard:
plastigauge reading:
Main Cap #1: (black/red) .0014”
Main Cap #2: (black/red) .0012”
Main Cap #3: (black/blue) .0011”
Main Cap #4: (black/red) .0012”
Main Cap #5: (black/red) .0011”

Dial bore gauge reading: Front / back of bearing
Main Cap #1 - (black/red) .0012”/.0011”
Main Cap #2 - (black/red) .001”/.001”
Main Cap #3 - (black/red) .0008”/.0008”
Main Cap #4 - (black/red) .0008”/.0009”
Main Cap #5 - (black/red) .0012”/.0013”

Port engine:
plastigauge reading:
Main Cap #1: (black/red) .001”
Main Cap #2: (black/red) .0011”
Main Cap #3: (black/red) .0011”
Main Cap #4: (black/red) .0009”
Main Cap #5: (black/red) .001”

Dial bored gauge reading: front / back of bearing
Main Cap #1 - (black/red) .001”/.0011”
Main Cap #2 - (black/red) .0011”/.0011”
Main Cap #3 - (black/red) .001”/.0009”
Main Cap #4 - (black/red) .0005”/.0006”
Main Cap #5 - (black/red) .0007”/.0007

Of course anything under .001” on the plastigauege was an estimate and anything in between .001 and .0015 were estimates based on how much the plastic squished. Just showing what I got via plastigauge vs what the actual measurements were. Black/red bearings I believe were in the middle of the road for size. So going up 2 sizes would have some large oil clearances

Just a reference, Yamaha does not post the size of their bearings (ex. .0010 over .0020 under) they just got by colors. I only had an issue with one of the rod bearings. I initially purchase all blue bearings for my rods. When measuring one rod was .0020” spec was max of .0016”. I dropped a size (color) to a black bearing, remeasured and got .0010” clearance. So not sure if the bearings are in .0010” increments or if that was just how everything measured out for me.