I have a Mercury 8 HP outboard on my dingy. I bought this motor new in 1993 and it has basically been problem free except once the needle got stuck in the seat after sitting through the winter (no big deal).
This year it would start but stall, then start and stall. I took the filter off and it was full of black crap. I cleaned it out, started the engine which ran for a minute or two then stopped again. The filter was full of crap again. I emptied the gas tank (it was full of new gas and
oil mix) and saw a bit of junk in the bottom and I also saw a piece of hose which I retrieved. The plastic hose just fell apart when I touched it. This was the drop down or pick up hose that picks the gas up from the bottom of the tank. Since there is no way to put a new pickup hose in the tank, I bought a new gas tank. I then realized that the black crap in the filter was coming from the gas line, more likely from the primer bulb in the line which is made of black rubber.
I removed the carb and filter and cleaned everything out very well. The engine now runs OK but the carb will need a complete rebuild kit before it goes back in the water next spring. I think that I also need a new gas line just to be safe.
While I was having these problems, a small-motor mechanic was being interviewed on TV. He said that he is very busy fixing small gas motors on outboards, lawn mowers, weed wackers, chain saws, snow blowers, etc. The ethanol in the gas is chewing up just about anything made of rubber. His advice was to make sure that gasoline stabilzer is used in any motor that is going to be left standing for any amount of time. I have always just run all of the gas out of any small motor including my outboard but I paid the price this year.
Wayne