2003 4 stroke 90 water in gear case?

The large O ring (4" od) that rides behind the reverse gear thrust washer seems to be undersized. it is not sealing the case. yamaha part #93210-85m97-00. has anyone ever have one shrink in size?

This seems to be a popular O ring for yamaha's, and fits many applications. Has anyone had any sealing problems with water leaks from this seal? I have ordered a new seal, but it has not arrived yet.

Can anyone provide an outside measurment for this seal, along with thickness? The one I took out is approx 3 11/16" od. with a thickness of about .220".

call manufacturer and get specs,and get rite o ring!!

You say it " seems to be undersize "--It will expand when the big nut is tightened.---------Look for issues like " cocked seals " under the water pump on the drive shaft.-------------Did you pressure test to find the actual leak ????

For what it is worth I figured out the problem. The engine is my brothers. several years ago a neighbor worked on the lower unit. He used a bearing housing from a yamaha 90 4 stroke and not a yamaha f 90 4 stroke. the f 90 is about an 1/8" larger in diameter. now the o ring seals.