Overflow gear lube reservoir

Folks. I need some thoughts please from those familiar with Mercruiser Bravo 3 outdrives. Last two times out my gear lube reservoir leaked out of cap - first time this has happened in three years since I bought it. The reservoir is the one with the red pin smaller cap on left side of pic. The level of tank is near but not over max line. Thx

I do not know your drive but if it never leaked before but is doing it now I would get it checked that a seal has not failed and is allowing water into the units gearcase.
Do you see ANY oil floating on the surface at the drive? THis clue is not a guarantee it is not leaking but is often a good clue it is.
They should be able to pressure test for a questionable seal. Get it hauled and find out. If water is getting in and it is not dealt with in a timely fashion the repairs will be expensive.

As a last question -- overfilled? I suspect this is not likely.

No oil floating at drive when moored at marina. My guess is that when I topped it off I'm spring the summer heat together with engine heat caused expansion. I remove oil from tank this weekend using a turkey baster, so will run it next weekend and if it happens again. Owners manual tells me this engine will slow down automatically if gear lube gets low. Thx.

Drain a sample off to look for water, it will be on the bottom, oil floats on water.

Don't assume a seal is not letting water in. It will be extremely expensive if you are wrong. Sure it will be a few bucks to test. It may not get low due to water entry.

Of course up to you. Good luck.

My guess/concern would also be water in your gear oil that is foaming up when run and causing the overflow

Was the drive recently filled? B3’s can trap air when filled causing them to burp. I would simply top it up (happened to me causing low fluid alarm to sound) Corrosion was my B3’s real problem, for that reason, I’d never own one again...

Maybe run the level a little lower than “max”

Yes I did pull the outdrive for annual maintenance etc. I've painted the outdrive with bottom paint plus have zincs on the Merccathode system should help with corrosion some. thanks for all comments here. Since it is under warranty I will run it in to dealer and let you know what they do.

Okay I ran the boat today out to calibogue sound about 2 hours round trip at 3500 rpm approx 21 mph. Cap tight and no leaks. Will still pull boat out and check for leaks. Thanks for all the comments.