I have a 1974 1500 inline six merc. I took the boat out today and it started fowling plugs on me. It looked like a lot of carbon build up was on the plugs. Does anyone have any suggestions as to y this is doing this? I thought water in fuel.
When was the last time you took a look at your plugs? Did it run better after you cleaned the plugs? How old are the plugs? Do you have a fuel/water sepparator and is my gas contaminated? Have you changed anything since the last time you ran the boat? Is the ignition system working properly? Just some questions I'd ask myself in this situation.
It does sound like the carbs are flooding. If you pump the primer, ofter the flooding will be obvious, likely on the outside of the carbs. If so, tear the carbs down and clean 'em up. Now rebuild them with new gaskets, new inlet needles and seats. Inspect the floats. the originals were foam which can disolve. Replacement floats are hard plastic, which can crack.
