Why Did My Mercury 35hp Outboard Just Stop Working
Posted in Ignition Systems | Asked on May 22, 2011
Hi, this god dam outboard, my engine has always been great until recently it started getting a little harder to start, then whilst out fishing my engine just gave up all together, 
( can anyone please advise me, i have check the fuel is getting through ok, i’ve had the flywhel off to check the magnets and electrodes are still ok (past experiece magnet broke and damaged electrodes) this all seems to be in perfect order, i’ve now ordered new spark plugs just to make sure even though i have a couple of old plugs here swapped spark plug wires with other ones, the only thing that i can notice any difference is that when testing the spark plugs the spark is’nt as intense as it used to be. impeller is new and working fine, engine is pissing well (atleast it was when it was working) any suggestion would be greatly appreciated.:o)
There are 2 Answers for "Why Did My Mercury 35hp Outboard Just Stop Working"
Hi, seems you have a couple of options, you say the fuel is getting through, but to where, to the carby or to the plugs and making them wet, if they are wet and you have a spark, and you have’nt sheared off the key on the flywheel then it should start, is it points and condenser or CDI ignition, if its points then the capacitor may have broken down and is running the spark to ground but still showing signs of a weak spark at the plugs, and sorry if you are not getting fuel to the plugs do a good job of cleaning the carby with compressed air, make sure all electrical connections are clean and secure, have fun, take care.
Back to basics. Compression, spark, fuel. If she has all three she runs, otherwise she don’t.
Is the fuel fresh, and the tank clean and free from water and debris?
Does the fuel line hold pressure?
Compression test will tell you if any of the engine internal parts have failed. PSI should be about equal on all cylinders (within 5 or 7% or so). Bad compression, you have to pull the cylinder head for inspection.
Spark test — not a “spark plug test” — get an inline tester (couple bucks at autozone), set the gap for 7/16″ (or 1/4″ if it’s an old school points/condenser/distributor type ignition), clip it to the engine block, attach the spark plug leads (one at a time) and look for a sharp blue spark while cranking.
Bad spark or no spark on a cylinder, post another question for the next troubleshooting steps. btw, this might have save you the trouble of pulling the flywheel.
Good compression and spark on all cylinders, good fuel pressureand fresh fuel, rebuild your carburetors.
I have found that it never pays to ignore symptoms (“…started getting a little harder to start…”)