Two Sheds
Member
Greetings all. I need some help! I have acquired an elderly Mercury 4hp 2 stroke single cylinder outboard as a non-runner. It hasn't run for at least 3 years, possibly much longer, and I do not know its history. The carburettor was gunked up as is to be expected so I stripped it and cleaned everything out in an ultrasonic bath. All the jets are now clear. The tank was dry, so I cleaned it and added fresh fuel. There is an inline fuel filter which is passing fuel through and the pipes from tank to carb are clear.
I put the carburettor back on and checked for a spark. There is one, but it is not particularly strong. I checked the compression and it is about 90psi which is not bad for a cold engine of uncertain years, I guess.
Despite much pulling, and ultimately removing the starter and turning it over on the crankshaft nut with a cordless drill, it will not even as much as give a cough. I even put a petrol-soaked sponge in the air inlet to the carb, to eliminate float chamber issues, and got nothing. So I am turning my attention back to the spark.
Now, one of the difficulties I am having with this motor is that I cannot identify its age, even less get a manual or any other information for it. The label on the transom plate has long gone so I do not have a serial number. There is a number on a core plug in the crankcase (9573199 - see pic 1), but I have not been able to interpret this on the Brunswick site or elsewhere on the internet.
So going in blind, and expecting to be checking out points and condenser, I took the flywheel off and found no such thing. See picture 2. So it seems to have electronic ignition. The wrapped component visible in the picture has the word "Exciter" next to it in the casting, and in the diametrically-opposed position on the other side of the casting, as you can see in the picture, is the enigmatic word "Light". In the bottom right of the picture is what looks to be a pickup that determines the ignition timing.
I am a bit clueless with electronic ignition, and in the absence of a manual, can anybody please enlighten me as to how to troubleshoot the system? I have a multimeter but don't know what to check or what values to expect.
Thanks all
Martin
I put the carburettor back on and checked for a spark. There is one, but it is not particularly strong. I checked the compression and it is about 90psi which is not bad for a cold engine of uncertain years, I guess.
Despite much pulling, and ultimately removing the starter and turning it over on the crankshaft nut with a cordless drill, it will not even as much as give a cough. I even put a petrol-soaked sponge in the air inlet to the carb, to eliminate float chamber issues, and got nothing. So I am turning my attention back to the spark.
Now, one of the difficulties I am having with this motor is that I cannot identify its age, even less get a manual or any other information for it. The label on the transom plate has long gone so I do not have a serial number. There is a number on a core plug in the crankcase (9573199 - see pic 1), but I have not been able to interpret this on the Brunswick site or elsewhere on the internet.
So going in blind, and expecting to be checking out points and condenser, I took the flywheel off and found no such thing. See picture 2. So it seems to have electronic ignition. The wrapped component visible in the picture has the word "Exciter" next to it in the casting, and in the diametrically-opposed position on the other side of the casting, as you can see in the picture, is the enigmatic word "Light". In the bottom right of the picture is what looks to be a pickup that determines the ignition timing.
I am a bit clueless with electronic ignition, and in the absence of a manual, can anybody please enlighten me as to how to troubleshoot the system? I have a multimeter but don't know what to check or what values to expect.
Thanks all
Martin
