I never said pre-purchase oil samples were worthless, I said they are of limited value and buyers often over react to the results. The OP is a perfect example of the value gained, he now has a full transmission warranty for his 400 mile ride home with his boat, how many of you got that when you bought? Hopefully he will report back on here the results of the sample taken after his trip home. I'd love to hear how his transmission is doing 6 months, a year from now.
I wonder if it would change any minds if he reports that it is all fine 6 months from now, and that you all over reacted?
While you guys seem to think it's unethical to not have dirty old oil in an engine when it goes up for sale, think about how easy it is for a truly unethical seller to fake the results. They don't even have to go through the work, expense and time of an oil change, they can just lie about the time/hours on the oil. Levels of contaminates that would be normal at 120 hours and 10 month old oil would be high if the oil actually had only 10 hours and 2 months.
Of course none of this matters on well maintained boats when a glance at the engine tells me the date of the last oil change.
I don't understand why the concept of oil analysis as trend analysis being far superior to it's use as a one time assessment of the engine is controversial. I think of it like the annual blood test the doctors take every year. If the results show that you have high cholesterol, how would you like it if your doctor over reacted, said "your going to die, you obviously eat a terrible diet, you're probably going to have a heart attack any minute! If you're lying to me about your diet, you're probably lying about smoking weed, cigarettes, and drinking excessively too!"
But no, your doctor wouldn't do that. What if you forgot to fast and had breakfast that morning and your blood sugar results were off. Should the doctor start you on insulin right away? No, of course not. He'd make sure the test was done properly (change oil and put a fair number of hours on it) then retest.
Even if your test results are out of spec, a doctor won't usually make a diagnosis without checking other things and repeating the results to make sure they are valid.
It's comparing the results over a period of time that tell if you have a gradually increasing problem or if it was a one time event that caused the result you saw.
I haven't even mentioned the problems inherent in the sampling process itself. You've got to get the tube down into the pan, but you don't want to suck from the very bottom either or you can pull sludge/debris into your sample and get a false reading, all while hovering over a hot engine in a (again Florida) often 130 degree engine room with sweat (sodium, water) pouring off of you in buckets.
But again I'll say it, pre-purchase oil analysis does have some value, it's great for renegotiating after survey, it can identify potential problems developing, but the results can also often be misleading. It's a snapshot, like taking a still photo on a crowded street. It will tell you who is there on the street, but you can't tell what the people are doing or how they got there, you need a video for that.
Every boat owner should be taking regular oil/transmission samples whenever they change their oil. Then this whole discussion would be moot as you can just show any potential buyers your oil sampling history.