1977 Merc 25SS Kill Switch Install?

[smirnoff]

Looking for some help to install a kill switch to run at vintage meet (now mandatory).

What type do I need (2 or 3 wire, diode or not, etc) & what terminals to install on?

Thanks in advance!

[ricmontoya]

2 wire switch, no diode, I have the later 25SS (the small all black, all plastic brain box), 1 wire hooks to the phillips head screw at the back side of the flywheel and the other to ground.

[dndsam]

On both the black box and silver box electronic setups, you can tie into the two wires coming off the trigger to connect to a two wire kill switch setup. I have both style motors and use am isolation block on the exhaust side of the motor to make the connections. I have attached a picture of one of my silver box setups, but works the same for a black box as Rick mentions above. If close up pics are needed, I can post later.

[smirnoff]

Thanks for the replies - close up will be very helpful to get it right the 1st time.

[ZUL8TR]

Does your 77 have a brown lead at the switch box that is tucked into the harness with an unattached end? My 73 25ss had that the with silver CD box. The brown lead (in my case ) was a default wire for the safety switch on the fish engines and it remained for the 25ss harness. For my switch I attached one lead to the brown wire and secured it to the block (insulated connection) and the other end of the switch attached to the shiny metal of the block (non insulated connection). When the switch is pulled off its hold down the ignition goes to ground and kills the spark. I believe what dndsam describes is the same thing on the engine port side where there is a junction connection for the harness trigger wires.

Also do not pull over this engine with the plugs out and they are not grounded to the block, bad for the CDI and could damage it. In such pull over conditions just disconnect the kill switch and the system goes to ground, safe move for the CDI.

[dndsam]

"Photo 2" is of the silver box that zul8tr references and the common connections off the isolation block as I referenced above. "Photo 1" is of the black box and I wired this one a bit different due to what I was working with when I acquired the motor. I tied in the 2 kill wires in with the trigger wires and used a quick disconnect to connect it with the trigger. Vibration has not been an issue work these connections loose as they are now.

If you have a black box style motor, you may want to use zul8tr or ricmontoya's suggestions and have the connections locked down. Hopefully this gets you started.

[smirnoff]

Thanks again, located the "brown" wire which leads to a phillips head screw just below the flywheel, as mentioned.