1973 Mercruiser 165 will not start

[Jedediahvivio]

I have tried swapping the ignition coil and I have tried swapping the points, condenser and rotor button. I have tried to get a spark from the coil to no avail. I am receiving 8-9 volts to the coil while cranking and 3-4 volts with ignition on. I do not know what else to try. Will someone please help me.

 

[nola mike]

Not sure of your exact wiring, 8-9 volts may be enough to have it kick, but 3-4 isn't enough to keep it running. First thing is to trace your coil (+) back to your ignition switch and see where you're losing voltage. You should have about 10v with the key on (if you have a resistance wire). You might run a jumper from bat pos to coil pos for diagnostic purposes and see if you get a spark then.

 

[Jedediahvivio]

I have tried swapping the ignition coil and I have tried swapping the points, condenser and rotor button. I have tried to get a spark from the coil to no avail. I do not know what else to try. Will someone please help me.

Not sure of your exact wiring, 8-9 volts may be enough to have it kick, but 3-4 isn't enough to keep it running. First thing is to trace your coil (+) back to your ignition switch and see where you're losing voltage. You should have about 10v with the key on (if you have a resistance wire). You might run a jumper from bat pos to coil pos for diagnostic purposes and see if you get a spark then.

I did try running a jumper and I still had no spark. Tried to open and close points while having jumper connected and hooked a plug directly to coil. Still nothing. I should trace the wiring next.

 

[GSPLures]

I have a 73 Merc 140, I was having some what of the same situation. Check all the electrical connections remove them and clean (even if they look alright) then make sure they are tight. From what you describe the issue is from the coil back which you said you swapped to check the coil. Bench test the coil out of the boat so you know it has good ground. If it fires you have a grounding issue.

 

[Scott Danforth]

first, clean your points
second, clean all your connections at the starter and the battery - both positive and ground
third, its usually never the coil

you should have battery voltage while cranking as the coil gets it voltage from the I/R terminal on the starter

you should have about 9 volts when running (voltage drop across ballast wire is about 3 volts)

 

[1960 Starflite]

I have tried swapping the ignition coil and I have tried swapping the points, condenser and rotor button. I have tried to get a spark from the coil to no avail. I am receiving 8-9 volts to the coil while cranking and 3-4 volts with ignition on. I do not know what else to try. Will someone please help me.

I've had that problem on my 140hp. As stated B4, clean, clean electrical connections. I found problem with fuses. They looked good but, slight film of oxidation on contact ends. With a meter they check fine, put a amp load on them an they wont carry a load. Marine is terrible for electrical gremlins.

 

[nola mike]

I did try running a jumper and I still had no spark. Tried to open and close points while having jumper connected and hooked a plug directly to coil. Still nothing. I should trace the wiring next.

Yes, trace the wiring but that isn't your only problem if it isn't starting with a 12v jumper. What's connected to the neg of the coil? Disconnect everything but the wire to the points. Actually, first disconnect everything except a jumper. Hook up a plug tester to the coil. Tap the jumper on a good ground. It should spark. If not, bad coil (or high tension wire) If it does, your problem is either that something is grounding the neg coil terminal (tach, shift interrupt, points assembly) or your points aren't making contact (check resistance across the points when closed and power off).