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Old 07-13-2010, 05:02 PM   #1
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Default maxum 1800 4.3 190 hp

had the boat 2 years and ive had the problem of the engine running on when ignition is turned off and the engine as been running for 30 mins + recently been putting redex fuel additive in every time i refuel and problem as stopped.
is there any one out there who as had the same problem and cure or is this a coincidence.
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Old 07-13-2010, 07:31 PM   #2
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CNT,

It is no coincidence, something is amiss.

Is the gas you are using the correct octaine rating? Has the engine been tuned up - using the correct spark plugs and gapped correctly? Is the timing set correctly? Is the idle RPM correct? Is the engine running at the correct temp?
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Old 07-14-2010, 08:18 PM   #3
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hi thanks for your intrest,
new plugs, distributor cap ,ignition sensor, plug leads, rotor arm and timing set to 10 deg before tdc engine still run on when hot......put redex in with 80 litres of unleaded petrol problem stopped immediatly, what do you think

regards chuck
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Old 07-14-2010, 08:51 PM   #4
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Chuck,

Although it is good to have had the dist cap, ign sensor, plug wires, and rotor replaced those won't have anything to do with the run on issue.

The octane of the gas does, the timing does (but not very much), as does the spark plugs. If timing was set to factory specifications - good. Are you certain the plugs were replaced with the correct ones, and gapped to factory specs? Let's assume they were. That leaves the octane of the gas and/or the running temp of the engine. If the engine is has been verified as running at the correct temp then all that's left is the octaine question.

Run on, aka pre-ignition, is caused by the fuel being ignited without a spark from the plugs. Low octane gas is more prone to pre-ignition than is higher octane gas. Combustion chambers or spark plug electrodes/ground straps with heavy carbon deposits can also cause pre ignition because the carbon deposits get hot enough to ignite the fuel. Even an engine with minimal carbon build up can experience run on if it is running too hot.

I'm not familiar with the Redex product but I'll guess that it is nothing more than an octane booster. Find out what the octane requirement is for your engine. If a higher octane gas is available try a tank of it without the Redex.

Dan
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Old 07-14-2010, 09:27 PM   #5
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thanks,
over here in uk petrol stations have only one choice of petrol and thats unleaded/green. what i'll do, is look round for higher octane fuel from some where else. we have been using a local petrol station near the coast holiday home , will look into your ideas
regards chuck
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Old 07-14-2010, 09:54 PM   #6
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go to the airport (aerodrome in england speak) and get some 110 in a gerry can..tell em it's for your go cart.....(they don't check usually)...then pour about half of a 10gal gerry can into the fuel tank of the boat...problem solved!!

actually most auto parts stores carry an octane booster...but the best way to start is to ensure that the tune up was done correctly....no vacuum leaks at the carb base or shafts...(check this by spraying soapy water around the base of the carb ....engine will immediately smooth out some)..temps running in the right range???..

SP
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