Greetings all. First time poster. I'm looking at a 1977 Tiara vacationer with 1600 hours on the engine. Sea trial went well, but noticed what looked to me to be significant gear lube floating around the bilge. Grey/muddy green in color. This would be the first inboard I will ever have owned. With that vintage system what might be the likely culprit if it is indeed gear lube? Want to figure that into my purchase price. Thanks in advance, CT