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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3401
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have 1999 mercury 50 ELPT 4 stroke. Every once in while,

Customer Question

Hi I have 1999 mercury 50 ELPT 4 stroke. Every once in while, when out on the water, after it's been running and I then shut it off, it won't start again. Just makes a humming/buzzing sound. Doesn't try to turn over, just the sound. A few times it happened I had to be towed in. Couple other times after waiting a bit it started. Doesn't happen every time I go out. Just kind of random. trying to figure out what it might be so I can try and repair myself. any help would be greatly appreciated
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.

Hello, my name is***** will assist you today.

There are a few things that this problem could be. You will need to have a good quality multimeter and a helper to troubleshoot this. Do you have these?

Customer: replied 1 year ago.
Don't have a multimeter, don't even know what that is. But I do have a helper
Expert:  Charles replied 1 year ago.

a multimeter is used to measure voltage. We are going to need to be able to, to locate the source of the issue.

Customer: replied 1 year ago.
Ok well don't have one of those. But can run to the auto parts store to get one. So u think it's something battery related?
Expert:  Charles replied 1 year ago.

It is something either in the charging or the starting systems. If you are going to the auto parts store, take the boat battery and have it load tested. That wil eliminate a step.

A digital meter is best.

Customer: replied 1 year ago.
Ok will take batter and have it load tested. If they say it's fine should I still get the device for us to further trouble shoot? How do I contact you back once I return.
Expert:  Charles replied 1 year ago.

All you have to do is reply the same way that you have been. I will be here until around midnight CST today and after 10 AM tomorrow.

Customer: replied 1 year ago.
Battery tested fine. Got the digital multi tester.
Expert:  Charles replied 1 year ago.

That was quick.

Reinstall the battery in the boat. Make sure that you put the red on the positive post.

Customer: replied 1 year ago.
Ok cleaned up the terminals and all is reconnected
Expert:  Charles replied 1 year ago.

Great. Check the power at the starter solenoid on the red wire. Red meter lead to the red cables on the solenoid, black meter lead to a clean ground on the block. Test it both with the key off, and then in the start position. Turn the kill switch off, so the motor will not start. Let me know what you get there.

Customer: replied 1 year ago.
Ok what setting do I out the tester on? ACV, DCV? And what number setting? And where do find starter solenoid?
Expert:  Charles replied 1 year ago.

What make and model is the meter, I need to get a look at it.

Customer: replied 1 year ago.
Performance tool w2974. Photo attached
Expert:  Charles replied 1 year ago.

20 on the DCV scale. The solenoid is part 9 in the diagram. It is on the front of the engine.

http://www.boats.net/parts/search/Merc/Mercury/1999/1F50412VD/ELECTRICAL%20COMPONENTS/parts.html

Customer: replied 1 year ago.
Is this it at top of photo
Expert:  Charles replied 1 year ago.

Yes that is it. Red meter lead to the post with the red covered wires on it.

Customer: replied 1 year ago.
Reads about 12.3 with key on or off
Expert:  Charles replied 1 year ago.

Did you turn the key to start to engage the starter?

Customer: replied 1 year ago.
Turned the key on but didn't crank it. Should I do that?
Customer: replied 1 year ago.
Drops to about 9.5 when trying to crank motor over. But hey at least it's cranking. When it's doing to humming sound there is no crank whatsoever.
Expert:  Charles replied 1 year ago.

Yes, I need to know what the voltage is with the starter engaged.

Customer: replied 1 year ago.
9.5
Expert:  Charles replied 1 year ago.

Ok, more the red meter lead to the Yellow tipped wire on the solenoid and crank the engine over again. Them move the red meter lead to the other end of the yellow wire at the starter, crank it over again.

You are looking for voltage that is very close to 9.5V at each test point.

Customer: replied 1 year ago.
Yep pretty close to that at both those points
Expert:  Charles replied 1 year ago.

Ok,

Your issue will be a failing starter. You can either replace that one with an after market one, have that one rebulit at a starter shop, or get an OEM starter. Do you need a part number?

Customer: replied 1 year ago.
How is it failing starter if it tested at around the 9.5 you said at each point?
Expert:  Charles replied 1 year ago.

You are getting good voltage at all the test points. What has to be happening is that when the starter gets hot from the engine running, the brushes do not make good contact with the armature, and therefore cannot spin the engine over.

That or the engine is locking up.

Customer: replied 1 year ago.
when you say 'cannot spin the engine over' would that lead to the 'humming/hissing' sound I described?I don't mind getting a starter if there's good chance that is problem and the symptoms/sound I am describing are indicative of a bad starter.And when you say I'm getting good voltage at all the test points would that indicate it's not something with the wiring/electrical between the motor and ignition? Sorta like it's getting plenty of power hence if doesn't work sometimes it's the starter locking up?
Expert:  Charles replied 1 year ago.

Yes. If the starter was engaging the flywheel, but unable to spin the engine over, it would hum. Good voltage is defined at as least 9.5V DC with the engine cranking over. We know that the battery is good, cables are good, solenoid is good. Only items left are starter or block. To eliminate the block, remove the spark plugs from the engine and look at the tips, are any of them slightly silver in color?

Customer: replied 1 year ago.
Will have to do that in morning and will write you then. Does it matter if buy aftermarket or rebuilt starter? Yeah if you could send me part number that would be great. How much do they run for cost? Pretty easy to install?
Customer: replied 1 year ago.
Also if I want to utilize you again how to I get directly to you?
Expert:  Charles replied 1 year ago.

Starter is part 1 in the diagram.

http://www.boats.net/parts/search/Merc/Mercury/1999/1F50412VD/STARTER%20MOTOR/parts.html

Aftermarket is

http://www.amazon.com/ARCO-Marine-5362-Starter-Made/dp/B000NJ4VCG

To get back directly to me, you can either request me in the question page or lace my name in the question line. I am only online after 7 PM CST weekdays and most all day on the weekends. I spend my day hours in a busy repair shop.

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