2003 225 Lower Unit Black and Tan

While preping the boat for our upcoming season and changing the lower unit oil my port motor oil drained dark brown (almost black) and the starboard engine was golden tan. My first thought was water intrusion but expected to see a milky color ? My next guess is to pressure test that lower unit to see if it holds pressure. Total time on motors about 400 hours and less than 50 since lower unit oil change. any thoughts? As always thanks for the help from this forum.

Other notes: no metal found in oil on either side and gear oil was changes last year one year ago

This is only speculation on my part. I wonder if exhaust gasses are getting in through a crack in the housing? I suppose it should show up on a pressure/vacuum check but, if that pans out then I would still be worried about a crack that opened up when the exhaust started flowing and heated the case. In that scenario, there might be enough positive exhaust pressure present to exclude water from getting in.

I will be very interested in what hondadude might have to say about this one.

Two other long shot possibilities - lower unit with dark oil could have overheated or a type of oil-eating microbe has gotten in there. If the oil is "burnt" it should have a distinctly different smell.

Did not notice a burned smell (but was not looking for it either). Thought I would run it for a few trips and change the lower unit oil again. Would have to pull the boat to pressure test the lower unit for a leak. Any other thought out there?