1983 Mercury BlackMax Starter won't stop spinning

Hello,

BlackMax is a 150HP.

My starter stays "on" while the boat motor is on.
I turned off the motor and it is a buzzing sound, presumably the starter.

I had to disconnect the negative battery terminal to get it to stop. Then, bumping the negative terminal with the wire will attempt to start the motor even if the key is off.

Is this something replacing the key on control box may fix? Or does anyone know the wiring schema to tell me how to test what's wrong with key on control box?

THanks,

Boat motor repair rookie

Re: 1983 Mercury BlackMax Starter won't stop spinning

It may just be a bad starter solenoid. Disconnect the small wire(s) going to it then connect the battery back up. If the starter still spins the solenoid is stuck closed. If it doesn't spin then you probably have a bad ignition switch.

Re: 1983 Mercury BlackMax Starter won't stop spinning

I agree on the solenoid but differ on the root cause. The solenoid is a high current copper switch made from 2 large terminals with flat tops and a flat disc mounted to a shaft with a spring. The power applied to the small terminals causes a magnetic field to develop around the shaft and sucks it down which makes the disc contact the other two terminals when starting the engine. The spring is supposed to return the disc to the up/non contact position when finished.

However, if the terminals/disc get good and pitted due to old age, they can weld themselves together causing your problem. Solution, new solenoid or take yours apart and burnish the contacts. The terminals can be turned around as only half of each makes contact and the other half is like new. Then file/polish the copper disc.

Mark

Re: 1983 Mercury BlackMax Starter won't stop spinning

Texasmark said:

I agree on the solenoid but differ on the root cause. The solenoid is a high current copper switch made from 2 large terminals with flat tops and a flat disc mounted to a shaft with a spring. The power applied to the small terminals causes a magnetic field to develop around the shaft and sucks it down which makes the disc contact the other two terminals when starting the engine. The spring is supposed to return the disc to the up/non contact position when finished.

However, if the terminals/disc get good and pitted due to old age, they can weld themselves together causing your problem. Solution, new solenoid or take yours apart and burnish the contacts. The terminals can be turned around as only half of each makes contact and the other half is like new. Then file/polish the copper disc.

Mark

Click to expand...

I have a 220 air compressor that did this. Finally had to replace the contacts because they stick together and the compressor would not shut off. Can't tell you how many times that thing ran overnight because of that.:mad-new:

Re: 1983 Mercury BlackMax Starter won't stop spinning

I really appreciate all of your advice.
If it is a switch, then is it best to simply replace instead of tinkering with it?

Also What is the best publisher for a repair manual?

Re: 1983 Mercury BlackMax Starter won't stop spinning

brandonjohnson said:

I really appreciate all of your advice.
If it is a switch, then is it best to simply replace instead of tinkering with it?

Also What is the best publisher for a repair manual?

Click to expand...

Yes on the replacement comment.

On the manual I have the OEM Merc manual and also subscribe to the Seloc online manual on this site. I find both lacking in some respects and use both.

Case in point, a day or so ago we were talking about an oil pump interconnect parts on a built-in oiling system. One respondent said that the parts breakdown shows the............... Well my Merc service manual had a parts breakdown on some things, but not the pump. So I go to the Seloc and there it is, showing all the parts he was talking about. I had the OEM for years. The Seloc subscription is recent and worth the money. But I'm not sure it alone will carry you. Just depends.

Mark

Re: 1983 Mercury BlackMax Starter won't stop spinning

Texasmark, I appreciate the advice! Especially on the SELOC online subscription. Thanks!

Re: 1983 Mercury BlackMax Starter won't stop spinning

Here is an update.
I took the small cable and disconnected it from the Starter.
Then, I bumped the disconnected battery cable and "NOTHING" happened.
So I was cheering and glad that I did not have to replace/rebuild solenoid.

But THEN, I reconnected the starter cable and bumped battery again. The previous experience of a constantly spinning Starter was NOT observed.
I thought battery was dead, but I left cable connected on battery and bumped the key at the control box.
The engine turned over.

So now I am confused to whether my starter solenoid is going bad or if my switch is going bad or has a short somewhere in the cabling.

I will watch it, and hopefully this was just a freaky instance.

But my question is, would this or could this only be an intermittent issue? Meaning, does a solenoid go All the way out or does it gradually go out?

Thanks team!

Re: 1983 Mercury BlackMax Starter won't stop spinning

Typical symptom of welding contacts. You temporarily unwelded them but they WILL weld again. You just don't know when or where you'll be.

Sorry for the bad news but it's good news as your problem will be gone. Stay home and watch TV on a Saturday night and use the money you would have spent partying on your new solenoid. Wink!

Mark