when to replace rod bearings

[rustybeater]

Hello, I am in processes of rebuilding my 1993 Johnson 90 horse cross flow motor because it chewed up a piston ring. My question is when is it necessary to replace the rod bearings. I priced a bearing kit by serria and it is about $500. I don't think my bearings look like they have over heated or anything but it does appear to have some wear. I just wanted to get someones opinion that has more experience.

 

[Silvertip]

What do the journals look like. It makes no sense to replace bearings if the journals are bad. If they are ok then it is a matter of just how worn the journal and bearing really are,. Break out the micrometer and measure. Can't tell from the pictures if/how much the bearing wear is.

 

[rustybeater]

ok so bare with me, I am kind of new at this. I understand that a car motor has the bearing journals that lock in the connecting rod but, on this the lower bearing goes directly into the connecting rod. I cant find the measurement of what the connecting rod is supposed to be. Mine read 1.689 the more and more that I look at these bearings I think that they do look like they have gotten hot so... I think I am going to go ahead and replace them.

 

[schematic]

those bearings will outlast your motor. They haven't suffered from overheat if the crank isn't destroyed. If the crank looks good the bearings are fine. Its the piston pin bearings and rods that need close inspection.
IMHO

 

[emdsapmgr]

If the rod bearings overheat, they turn blue. At that point they are scrap. If they aren't a blue color or pitted, I'd reuse them.

 

[F_R]

I agree, they just don't wear out. Slight discoloration is not cause to replace them . If they truly were turned blue from overheat, you would have a lot more problems than just the bearings. Anyway, the only reason they would get hot would be if it was ran without any oil. As I said, if that happened, everything else would be shot also. The pistons are the first thing to go in an oil-starved engine. You have to consider the crank, rollers, and con rods a single bearing set, concerning wear or damage. True wear will show up as flat spots, pitting, chipping, etc. If they are worn size-wise, you would see other physical damage.

 

[rustybeater]

Thanks everyone for the responses.