Outboard motor starter stuck
 

I am not the best with electrical systems.

Yesterday morning went to fire up the 2003 Mercury 50 ELPTO two stroke.

I turned the key starter engaged the motor and spun as it should. The motor didn't start after a few seconds so I turned it off primed the ball and tried a second time, same thing. On the third try the starter engaged but when I went to turn the key off the starter stayed engaged and kept cranking.

I could not turn it it off. I had to disconnect power at the battery. If I touch the cable back to the battery the starter will reengage and crank until power is cut.

What do you guys think, bad key switch, solenoid, relay?

Again, I am not verse in electrical systems so voltmeters and such are Greek to me. I really should learn?

corroded component

Definitely a bad starter solenoid.

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Clean all contacts.....boat motors need love long time.

Another vote for solenoid going bad, it will stick "on" (plunger pulled in on solenoid so gears pushed out/engaged with flywheel) resulting in the situation you describe. There is also an outside chance that the actual shaft that your starter gear slides on might be gunked up, but usually that would result in a failure where the drive does not engage whereas yours won't disengage.

On my outboard (late 90s Mercury Offshore 125 2smoke) the starter solenoid died this way and I was able to locate an entire starter including solenoid for around $100, but you can buy the solenoid as a standalone item as well. Not rocket surgery to replace but do be sure to disconnect power (including from any sort of house battery/ACR system!) before you start spinning wrenches.

That's what I was thinking. Just needed conformation.

Definitely not a gunked up shaft. As soon as power is cut the pinion gear retracts. Add power the gear pops up and engages, remove power it retracts. That's why I ruled out starter failure. I think the problem points mostly to the key switch or solenoid? I'm leaning toward solenoid.

Interesting, so just went out touched the battery cable to the battery expecting the motor to try and start. Nothing. So I properly attached the cable. Lifted the hand throttle turned the key. Fired right up half a crank no starter issue. Gear popped up turned the the motor retracted.

I did that three or four times no issues. So now what?

My guess: your solenoid stuck before, and it appears to be unstuck now.

It still needs service/replacement. It will fail again, the only question is when.

I suspect if you disassemble it the failure mode will be obvious.

Not sure how boat starters work but in cars the key switch does one thing: It overcomes a return spring and pops the starter drive gear out using the solenoid.
That's it.
(Solenoids pop a shaft in and out.)

When the gears are fully engaged with the solenoid at the end of it's travel, this closes another switch inside the solenoid: A heavy duty contact which sends current though the starter to turn it.
This happens only when the solenoid is fully extended.

If the solenoid is moving in and out it should be okay. They are usually the first to go.
I'd suspect the key switch or sliding shaft being gunked.

A very very distant possibility is the gears are so cupped they are getting stuck together but it's doubtful because of the starter overdrive disengage mechanism which retracts it when the engine turns faster than the starter.