1989 Johnson 48 SPL won't shut off

I bought a 1989 Johnson 48 SPL. The seller started it on a stand with muffs. It started fine, ran great, pumped water and then he shut it off using the red switch on the side of the block. It came with controls. So I mounted it, started it and then when I tried to shut it off using the key it just kept on running. So I pulled the tether cord stop but it kept on running. I then went to the engine and shut it off that way. I replaced the key switch but that did not solve the shut off problem. I remove the wiring cover on the side of the motor and find a cobbled mess on the rectifier. Apparently the red wire on the rectifier got so hot it melted the insulation off and about two inches of the wire is missing. The previous owner used a short section of audio speaker wire to patch it. I have a rectifier ordered and will be replacing the old one on Sunday.
Would this be why it won't shut off using the key?

Thanks Pappy

I wonder why that red wire melted on the rectifier

I've got a 1991 48 spl if you need me to pop the cowl and confirm anything for you.

Stumpalump said:

I've got a 1991 48 spl if you need me to pop the cowl and confirm anything for you.

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Thanks
Where is the black with yellow tracer wire grounded to the block?

Not having a schematic and it being dark out what I saw was the black wire with yellow tracer starts under the flywheel. It connects under all off the terminal screews in the junction box with its own large black rubber connector. From there it enters a harness and goes under the back of the motor to that huge round red connector on the port side. That goes to the throttle and switch assembly and probably the battery? Remember it's dark here. Guessing the key/deadman switch or whatever is what eventually provides the ground. Where it comes back to the block I did not get into but that ought to get you on track. I'd just throw a ground on it from any point and watch it die. Then find the wire on the key and or deadman that goes ground when off and make sure it's connected to it. Let me know if you need any other peeks.

Stumpalump said:

Not having a schematic and it being dark out what I saw was the black wire with yellow tracer starts under the flywheel. It connects under all off the terminal screews in the junction box with its own large black rubber connector. From there it enters a harness and goes under the back of the motor to that huge round red connector on the port side. That goes to the throttle and switch assembly and probably the battery? Remember it's dark here. Guessing the key/deadman switch or whatever is what eventually provides the ground. Where it comes back to the block I did not get into but that ought to get you on track. I'd just throw a ground on it from any point and watch it die. Then find the wire on the key and or deadman that goes ground when off and make sure it's connected to it. Let me know if you need any other peeks.

Click to expand...

Thanks again
I will do that

Pappy said:

On the back of the key switch you will find the Black/Yellow on a raised terminal vs the other connections. This was done to help prevent carbon tracking from the high voltage Black/yellow lead to the ground terminal in damp conditions.
When the key switch is turned to the off position the Bl/Y is connected to ground and shuts off the ignition.
A simple check with an ohmeter while the engine is not running will tell you if that connection is intact or not without having to pull the key switch.

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I have replaced the key switch last weekend. I was back to the engine again today and replaced the rectifier. I looked for the Black/Yellow wire to see where it would be grounded to the block. I had no luck in finding it. So I am going to take it to a marine mechanic and get it sorted out.
Thanks for your help. Much appreciated.

Pappy never said the wire should be grounded directly to the block. It goes to the key. The wire should have 300v on it when running and it should be at ground potential when off. The key switches it to ground when off. Ground is ground and it could come from a lot of places but eventually it does wind up on the block and on the neg batt terminal thru different wires. Do you have a volt ohm meter? Can you read the 300v at the key? Is the key grounded when off? If yes then your fixed. keep at it.

Stumpalump said:

Pappy never said the wire should be grounded directly to the block. It goes to the key. The wire should have 300v on it when running and it should be at ground potential when off. The key switches it to ground when off. Ground is ground and it could come from a lot of places but eventually it does wind up on the block and on the neg batt terminal thru different wires. Do you have a volt ohm meter? Can you read the 300v at the key? Is the key grounded when off? If yes then your fixed. keep at it.

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I don't own a volt ohm meter. I misinterpreted what Pappy was saying about the ground. I'll give it another try to find the problem.
Thanks

Been a while. The mechanic found a break in the black and yellow wire. The motor starts and shuts off fine now. The mechanic also suggested that I replace the prop. Replacing the prop sure made a performance difference. The best top speed I could get was 26 - 27 miles per hour but with the new prop the top speed increased to 30 miles per hour. I did not think that the old prop even with the many dents and a couple very small chunks missing on the blades edges would decrease the speed that much. Getting on plane is much quicker also.
Again thanks to all who replied to my question.

Sounds like you killed two birds with one stone. Everytime I buy a prop or get one refurbished I'd wish I had done it sooner.