I have been running HP marine in my Evinrude 300 on the lean oil setting for over two years. at least 300 hours of use. My dealer said the spark plugs look cleaner than most and almost did not need replacing after 300 hours. We opted to do so as we were going to put another 300 hours on it before the next service I burn 1/2 tp 3/4 of a gallon each day so XD 100 was adding up. I bought 3 cases of gallons when Amsoil offered free shipping. I was down aroind $30 per gallon where XD100 runs $44 to $48. at the local marina.
I have a 2007 Yamaha VMAX 150 HP on my saltwater flats boat. I was using the Yamaha Lube, but the Amsoil product is superior. I have less smoking, and less consumption with the he Amsoil. It is noticeable. I have now used this product for a year, so it isn't a new phenomenon.
I ran 6 gallons of Amsoil mix at 1/2(4oz) Normal mix is 8oz per gallon There were no signs of insufficent lubrication Motor didn't smoke quite as much. Of course it wouldn't with only 4 oz. I didn't pay attention to any oil globs coming up from below water line that is present on starting a cold motor with an 8oz mix. So that is still pending observation. I don't think I would go as low as 2oz/gallon though.
As a prior engine builder and worrying about engine failure from worn, rod bearings, piston rings, cylinder wall damage, I learned with Amsoil pure synthetic oil there was NO visible wear after numerous races on the engines. I use nothing but Amsoil in all my gasoline engines.
Bought a brand new 90 HP Evinrude Etec outboard motor this year. The Evinrude dealer told me they put AmsOil Hp marine Synthetic 2-stroke oil in the motor. Evinrude will still cover on warranty. The dealer said it's a lot cheaper than buying Evinrude XD100. Works GREAT! No Problems with this oil.