hi, i'm slowly but surely working thru some issues with this l6 165 mercruiser and pre alpha one (1978). I had water in the gear oil and discovered leaking seal around the lower shift shaft, replaced shaft and seal and that now seems fine (thanks bt doctor for advice). I also changed the gimbal bearing and u joints, all good. automotive ujoints were $18 each compared to $100 each for "marine" ones! took of ujoint bellows and inspected, it was good(only about 3 years old). also changed the lower shift cable while I was at it. the only problem I seem to have left is the engine wants to die after about a half hour of use. this happened the first good run I had this year and I discovered about a cup of water and rusty gas in the water separator. changed that and the filter above the fuel pump. I figured that would do it. not so lucky, changed the ignition coil as I heard these could overheat, still no good. the tank vent is not clogged, taking cap off tank doesn't help. I drained the tank and the gas came out clean eventhough I was rocking the boat and only about a spoonful of water in about 8 gallons of gas. the new water separator is also still clean and no water. I did notice the old filter on top of the fuel pump was crushed down as if a lot of suction had been applied (there was no spring on top), I checked the new filter after a couple of uses and noticed it too seemed to be squat down a bit. the filter up at the carb is clean. any ideas would be greatly appreciated as i'm running out of ideas (not to mention money).