1975 Merc 850 no spark

[seanmnew]

Long story short, bought a boat on the cheap from a guy with an 85hp Merc on it. The owner previous to him had the engine rebuilt and the guy I bought it from took it out on the lake, ran perfect. Tried to start it up to get back to the ramp and wouldnt start. Did a check at home and there was no spark. He didnt have the knowledge or patience to do anything with it so sold it to me.

I looked the motor over, cleaned up and repaired all electrical connections incase one of them had caused an accidental ground (nothing obvious that I saw). I did look inside the cap/rotor and they do appear to be worn down and coroded a bit. Spark plugs are in good shape as is everything else that I can see.

Two questions:

1.) Does anyone know where I can get a new cap/rotor combo? They seem to be impossible to track down

2.) Does anyone know if there is anything else I should investigate or any checks I should do?

I am not new to motors at all but I have no experience with outboards. Thanks!

 

[washingtonmike]

On some of the old Mercurys there is a mercury switch that wont let you start it when the motor is up I have seen them move and then you will not get spark I would look into that

 

[seanmnew]

On some of the old Mercurys there is a mercury switch that wont let you start it when the motor is up I have seen them move and then you will not get spark I would look into that

I did just this, and no luck. I checked the resistance of all wires and they were good after I repaired any cracks/breaks. My question, when the key is in the ON position shouldn't there be power going from the switch box to the coil? I checked and there was none. Which leads me to believe the switch box is out. Is that a correct assumption?

 

[Mi duckdown]

Sean. Serial number? If were you I would purchase an OEM service manual. It tells you Most everything you need to know about that motor.

 

[Chris1956]

Sean, That OB ignition is not like an automotive. There will not be any power to the coil, with the ign on. When the trigger fires, the switchbox will dump high voltage into the coil, to produce spark. Go to the CDIElectronics web site and run the ign test for your motor. It will tell you if the switchbox and wiring are good.

 

[seanmnew]

Serial number is 4099xxx, it's a 1975