During my last two long trips (150 miles and 72 miles) without much wind, the original Atomic 4 in my 1969 Columbia 28 has stopped running a couple times after several hours while at speed as if the ignition had been turned off. I've also noticed that the engine has lost alot of power when in gear (it won't go past 2000 rpm) and makes a knocking noise when run at higher rpms in neutral. I think it could be one of the valves because when I checked the newest spark plugs after the failures, the fore plug was very dirty. I cleaned all of the plugs and the engine ran, albeit not more than 2000 rpms in gear. Upon returning to port on the last trip, I checked the dirty plug and it was dirty again after only three hours running. Everything else seems to be fine (i.e. cooling system, electrical, starter, oil pressure, fuel, etc.). I also recently put a few ounces of Marvel Mystery Oil in the gas tank, but noticed no change in performance.
A little history about the engine. When I bought the boat two years ago, the engine hadn't been serviced in at least 4 years. I serviced it myself (new plugs, alternator belt, oil change, fuel filter, etc) and have been servicing it myself on regular intervals.
Any suggestions about what the problem might be would be helpful. Do you think I'm correct in assuming it could be a stuck piston or bad valve? Could it be something simple like needing lead additive or octane booster in the fuel?
Thanks for any help you can offer.
A little history about the engine. When I bought the boat two years ago, the engine hadn't been serviced in at least 4 years. I serviced it myself (new plugs, alternator belt, oil change, fuel filter, etc) and have been servicing it myself on regular intervals.
Any suggestions about what the problem might be would be helpful. Do you think I'm correct in assuming it could be a stuck piston or bad valve? Could it be something simple like needing lead additive or octane booster in the fuel?
Thanks for any help you can offer.
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