I am having a problem with one of my motors in a twin engine setup. I am losing 300 rpms on my motor, it runs fine for a while than it acts up with the rpm drop. I have had the identical problem before and have cleaned and soaked my carbs and this has always fixed the problem, not this time. I have had my carbs cleaned and soaked, I have changed my spark plugs, changed the primer bulb and have inspected the fuel hoses and none of these fixes has worked. I have had the same problem many times but a good carb cleaning has always worked but not this time. The only clue I found is when i changed the plugs, five of the plugs were dark like they are supposed to look but one plug was much dirtier than the others and had a bunch of build up around it. These plugs had only 20 hours of running time on them. I thought it may have been the problem but after changing all the plugs, the problem has continued. Does this mean that there was no fire on this cylinder sometimes which would have caused the dirty plug? Could it possibly be a coil failure or possibly a bad spark plug wire or could it be fuel pump related? I also have Racor water seperating filters installed on my motors which i changed at the beginning of the summer, should i try replacing again? Could my carbs need to be soaked longer or could something have been damaged by the mechanic who broke them down? Any suggestions or questions are greatly appreciated. <br />Seahorse and 12 footer thanks for the earlier suggestions more are welcomed.
