1985 yamaha 40hp spark issues

[rscottdds]

I have a 40hp yamaha that has been sitting unused for about 10 years. I pulled the plugs, lubed the cylinders, turned the fly wheel and put in new plugs and it started right away.
One of the carbs was leaking gas so I cleaned it and the other two carbs and then it wouldn't start. None of the plugs had a spark. I checked the kill switch and it looked OK. I checked the wiring evereywhere and all looked OK but it still had no spark. I took apart the throttle assembly and messed with the kill switch and it started. It could have been a coincidence though as I messed with a bunch of things.

It started about 10 times after that then quit again. Messing with the kill switch didn't help this time. I'd like to bypass the switch to rule that out as a problem. Can I just disconect it or do I have to connect the wires together? If its not the kill switch, any other ideas on wht to do?

Thanks,
Robert

 

[robert graham]

Re: 1985 yamaha 40hp spark issues

Well, I'm no expert here on the electricals, but there's the ignition swith, the emergency cut-off switch(lanyard) and the neutral safety switch that disables the start circuit while in gear. Sounds like it must be in one of those or their wiring or fuses. There's so much moisture and humidity in the marine environment that electrical contacts and connections tend to get just a touch of corrosion to stop the circuit. I've had these issues with the in-line fuses getting a white corrosion film on their contact points, just clean/polish it off and a bit of grease to keep out moisture. Good Luck!

 

[rscottdds]

Re: 1985 yamaha 40hp spark issues

Thanks. Anybody have a wiring diagram for these switches?
-Robert

 

[99yam40]

Re: 1985 yamaha 40hp spark issues

Disconnect the main harness at the motor and then use a jumper to hit the starter . If the problem is in the remote then the motor should fire when you disconnect the main harness, but be ready to find a way to turn the motor off as you have disconnected the key switch turn off operation also. Disconnecting plug wires from spark plugs and hooking them up to a spark board would be the best way to test.

 

[rscottdds]

Re: 1985 yamaha 40hp spark issues

Disconnect the main harness at the motor and then use a jumper to hit the starter . .

Did the above and no spark. Now what? I tried looking around the engine compartment for anything loose, unplugged or rusted. Everything looks normal. Stator? How do I test that?
-Robert

 

[99yam40]

Re: 1985 yamaha 40hp spark issues

Probably need to find a service manual for that old motor to see what it says, I have no idea if that thing has an ignition system like the newer ones or not.
Newer ones use a peak reading voltmeter to read the inputs and out puts of the CDI to make sure they are within spec in manual, or a DVA adapter and a regular voltmeter

If the inputs are good but out puts are not then the CDI could be bad.
The key and kill switches ground the wire to them from the CDI , that take the CDI out puts to ground to stop the sparking
If you can identify that wire and disconnect it from the CDI you will eliminate that wire being shorted in the harness

 

[rscottdds]

Re: 1985 yamaha 40hp spark issues

Thanks for the help. What would the most likely cause for no spark be if its not from the remote ignition system? I'm pretty sure when I got spark it would be from all plugs and when I didn't get spark it wouldn't spark anywhere.
-Robert