I have a 1986 Merc 25 HP with elec start and remote throttle/shift control, and a steering wheel.

About half the time the key switch and the safety lanyard switch will NOT kill the motor and I end up just pushing in the key choke until it sputters dead. I have a SELOC manual for 65-89 Merc Outboards repairs, but not sure what part(s) I might need to check and in what order. I think it has something to do most likely with the black-yellow wire and maybe the safety switch or the key switch, but is there a good way to test them or other way to go with this intermittent issue, or better way to kill it when it happens? There does not seem to be a pattern to when it works vs. when it fails. Where is a good place to get parts that I might need please?

IFFFF I am reading the above mentioned manual correctly, in the back it shows wiring diagrams, etc. On pg A 47 it shows the diagram for models including mine (model 25 electric), but it also says "All models equipped with tiller handle, ignition key/choke panel and remote control." Is this mine eventho I have no tiller handle, and why would you have a tiller handle and a remote control? Tiller would be just for steering ? I ask this in regards to the diagram and the 10 amp in-line fuse it says I should have in the red wire. When I got it from the last owner it had a 30 amp fuse in there...what is the proper size please, and is this diagram indeed for my motor?

Thanks...FRD

as an electrician I would use an ohmmeter to check for continuity at the key switch while cycling the key from off to on and back to off. you should lose continuity in the off position. If you do not, you may want to change out your keyswitch. Your lanyard will be in series with the run circuit. It also may have corosion inside the switch and not breaking the contacts. You can also check this with your ohmmeter.