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nissan marine 18

2007 4 stroke. idled fine in driveway. put in the water and didn't run under a load then died and wouldn't restart. cleaned and then replaced carb after same thing happened. wont even try to start now with new carb, also replaced the coil pack for the plugs. compression and spark seem good. Could it be the CD unit?
 
Well-----It should have run with a " new carburetor " I would say.-------But what other trouble shooting was done if any ?----Does spark jump a gap of 8 mm ( 5/16" ) or more , yes or no ?
 
model number NSF18B2

Well-----It should have run with a " new carburetor " I would say.-------But what other trouble shooting was done if any ?----Does spark jump a gap of 8 mm ( 5/16" ) or more , yes or no ?

When i say "new carb" i mean purchased brand new after cleaning the old one like 10 times to make sure that wasnt the problem. put on a spark tester and saw spark however it was the first time using one of those and i thought it would be more obvious. took out the plugs the other day after cranking on it. one did look a little wet.
 
The fact that it will run then die, and not restart puzzles me, maybe flooding? At one point it would idle perfect in neutral, then as soon as shifted in gear it would drop rpm and want to die if throttle not applied.
 
I would say it is NOT a carburetor problem then.------Sounds like it may be running on one cylinder.------Do the spark gap test with a proper tester.----Look / test in a dark room or at night to really see spark quality.
 
Will do. If only running on one cylinder what would be next to replace? I recently replaced the ignition coil and wires, ill get some new plugs.
Thanks for the help.
 
You need to learn some simple testing procedures to determine what is wrong.-------Guessing / replacing parts / cleaning a carburetor 10 times gets EXPENSIVE in $ and time wasted.
 
ive tested compression so that tells me its not valves or rings, i know its getting good fuel, i know carb is in good shape, brand new coil. So that leaves spark. Even with one firing it should at least "pop" every now and then. Its not even trying.
 
See post #6----Ask if you do not fully understand the concept of this ignition output test.----Check oil pressure switch .----Check kill switch.
 
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Ok that establishes the condition and power of the spark.-----Remove sparkplugs and put a few drops of gasoline into each plug hole.-----Install plugs and try to start it.------What happens ??
 
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