Started my 3.0 Mercruiser today, had flame shoot out carb, started and ran fine but diesels when turning it off. Had engine rebuilt (aprox 5 hrs on it) . Wondering if timing might be off? Any Ideas??
Check you spark plug connections. You may have some wires crossed. Definitely check the timing. Obviously, don't run the engine until you check it out. Hy
It's probably because your idle speed is too high. You should be around the 700 rpm range. If it's too high you will have run on. Your idle mixture screws may be off too. Do not let the boat diesel. If it does turn the key back on to start immediately before you damage the engine. Run on can also be caused by carbon deposits in the combustion chamber but check your idle first.
You may want to peer down the carb and see if it's leaking. If you have never rebuilt the carb, it may be a good ounce of PM. Good on rolling up the sleeves.
There is your problem, you can expect it to diesel anytime the idle is above 750. You should be idling at around 700 rpm in neutral. Then it will shut off. The other thing is to let the engine idle a minute or two to cool down after a good run.
