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Author Topic:   '86 Merc 150 - Starter won't stop
Buckda posted 08-01-2005 05:36 PM ET (US)   Profile for Buckda   Send Email to Buckda  
Had the boat out at the beach on Saturday afternoon/evening with a friend.

When it was time to go home, I started the motor (no problems) but while I was up in the bow retrieving the anchor, I could hear a hum that was not normal. I stopped and re-cleated the line and went back to (try to) turn off the motor. It stopped when the ignition was turned off, however the starter motor kept spinning, until I switched the main battery switch to "off."

Once I tried to turn the switch back to "1," the motor automatically engaged and tried to start the enging (ignition still off, happened both with and without key in ignition). The gear on top of the starter motor that turns the flyweel was "stuck" up/engaged. I removed the flyweel cover and sprayed this with some silicone spray and eventually when I threw the battery selector switch, it fell on it's own and didn't cause a problem. I then turned the motor on and went back to the front...same symptom. I went back and tried to turn the motor off again, no can do without killing the battery power from the main selector switch (even then the engine will run unless you turn the key off).

Did it again, and it's getting dark, so I decide to idle towards home (about 10 miles up the lake). Eventually the problem went away and did not recurr at the ramp, nor at any time during my boating on Sunday.

Is this just a Gremlin in a 19-year old ignition system, or is there something I can do to solve this problem? (Obviously, repower is the ultimate solution...and it's still in the cards, but I'm looking for a short term solution).

I've had some high volt readings lately on my multimeter taken at the batteries (pegged at 16V), however I'm not getting abnormally high readings on my GPS/Fishfinder combo (14.5 V) and I've never taken any baseline readings to compare what my new panel meter is telling me.

This symptom occurred last year just once as well, and I had since replaced the ignition switch since it happened to basically fall apart on me the next weekend in some really rough weather.

rtk posted 08-01-2005 06:44 PM ET (US)     Profile for rtk  Send Email to rtk     
Is there a solenoid before the starter? A bad solenoid that keeps the high current circuit closed will result in current always being supplied to the starter.

A bad ignition switch could be continuously closing the circuit when in the off or run position, or the solenoid itself will not open the circuit when you turn the key to off or run.


Buckda posted 08-01-2005 07:04 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Thanks Rich -
I'll check that out. Sounds like if that is the case, it is an intermittent problem and I should perhaps replace the solenoid as a precautionary measure?


rtk posted 08-01-2005 08:30 PM ET (US)     Profile for rtk  Send Email to rtk

Dave, here is a nice simple diagram of a typical starting circuit.

You can try to troubleshoot the problem too before you replace parts.

Remove all the wires from the solenoid so there is no electric connected to it. Using a multimeter, check for continuity between the two large lugs of the solenoid. There should be no continuity, or an open circuit when the solenoid is not energized. If the circuit is closed, or there is continuity, then the solenoid is bad.

If the circuit is open, then you can check the key switch. Hook up the two small wires on the solenoid, do not reconnect the heavy gauge cables, turn on the battery switch. With the key in the off position, check again for continuity between the large lugs. With the key off there should be no continuity, or an open circuit. If there is continuity then the key switch is energizing the solenoid in the off position and is bad.

Sometimes just tapping the solenoid with a screwdriver end will free it up too. As they say, the hammer is the mechanics best friend. When all else fails just beat on it!
It is a temporary fix but might get you off the water.


Buckda posted 08-01-2005 10:01 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Excellent link - and thank you.

I have to admit, there are times that I really feel like a dummy here, but I can't even begin to tell you how much I've learned just being on this site for the last few years..information like that makes it possible - thanks again!


Chuck Tribolet posted 08-01-2005 11:52 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Is it still doing it? If it stopped, it may be because the
problem fixed itself or (worse) because it burned up the
starter like happened to a friend of mine. His problem was
the switch.

I'd first check for a stuck starter switch (recent Merc seem
to have a lot of these, and you just replaced yours). Then
I'd check for a stuck solinoid.

You can do both of these at the solinoid. There will be a
thin wire and thick wire to solinoid. When the problem is
occuring, take your multimeter (keep it on the boat), check
for the voltage between the thin wire and ground. If there's
voltage there (any more than a little), it's the switch or the
wiring from the switch to the solinoid. If not, it's
probably the solinoid.


Buckda posted 08-02-2005 09:00 AM ET (US)     Profile for Buckda  Send Email to Buckda     
Thanks Chuck.

There is no way for me to tell until I get access to the boat again (on Friday). I keep the boat 90 miles away in SW Michigan. Running over for an evening of troubleshooting in Chicago traffic is not an option.

I do appreciate the help, and I'll check both. I keep my multimeter aboard the boat at all times.


rtk posted 08-02-2005 01:15 PM ET (US)     Profile for rtk  Send Email to rtk     
You are very welcome, hope it helps to solve your problem.

Chuck's suggestion to test while the problem is occuring is very good also. Intermittent electrical problems can be tough to isolate.

On an old boat I had with twin inboard motors, changing solenoids and voltage regulators was basically an exercise in annual maintenance. They were real cheap, so I always kept a couple spares around and just changed them when there was an indication of a problem.

If the solenoid is old, it may be a good idea to just change it while you are playing around back there if the part is cheap enough. Since the boat is 90 miles away you may want to arrive prepared with the parts if there is not alot of Mercury dealers close to the boat, save alot of time locating the parts.

If it were me, I would probably just buy a key switch and solenoid if the parts were under around $50.00 or so. Given the problems with the Mercury switches and the inevitable solenoid going bad it is not a bad idea to have spares on board if it winds up you do not use the new parts.

I too have learned alot from this site. It is an excellent tool in fixing and maintaining Boston Whaler boats.

The addition of the Small Boat Electrical section of the forum is great. Electrical problems and upgrades are a significant part of owning an older boat, and I think this section will help greatly. Thanks Jim!


jimh posted 08-02-2005 09:42 PM ET (US)     Profile for jimh  Send Email to jimh     
It sounds like your master battery disconnect switch came in very handy. I think they are always a good addition to a small boat electrical system.

Current to the starter motor is supplied via its relay or solenoid (as they are usually called when associated with a starting motor). If the motor continues to run after the ignition switch is turned from the START to RUN position, there are two possible causes:

SOLENOID--the solenoid has suffered a malfunction. It could be as simple as the contacts of the solenoid welding together. This can happen with relay contacts that handle a lot of current. This is a mechanical malfunction and the relay is not operating by electro-magnetic force--it is just stuck.

IGNITION SWITCH--the ignition switch malfuctioned and is sending current to the solenoid even after you move from START to RUN. This causes the solenoid to remain closed from electro-magnetic force.

I would not let the starting motor run too long. They are not designed for long periods of use, although if the flywheel gears are not engaged there will not be much load on the motor.

There has been some mention of problems with the ignition switch assembly on Mercury outboards. However, before replacing this you should verify it is the problem. Even if it is the problem, try a few sprays with WD-40 to see if this can cure the problem in the ignition switch assembly.

If the solenoid is the problem, it is probably best to replace it. It is not facile to repair heavy current contacts which have become welded together. You might be able to get a used one off a junked motor with a blown power head.

Buckda posted 08-10-2005 06:07 PM ET (US)     Profile for Buckda  Send Email to Buckda     
FYI - I isolated this as a solenoid problem on the starter circuit. (Thanks for the link to the diagram!)

A new solenoid retails for $18.95


jimh posted 08-10-2005 06:17 PM ET (US)     Profile for jimh  Send Email to jimh     
Dave--The price of the new solenoid has to be the best bargain in marine repair part history! I am pleased to hear that you diagnosed the problem and are repairing it yourself. Good work!
rtk posted 08-10-2005 11:25 PM ET (US)     Profile for rtk  Send Email to rtk     
A $20.00 part, plus some time to fix a problem is always a good thing. Glad it worked out. The diagnosis you did applies to most basic 12 volt systems too.

If you can troubleshoot that you can troubleshoot most basic 12 volt system problems.


Buckda posted 08-15-2005 12:20 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Just to close the loop - I installed the solenoid this weekend. Doing a solenoid swap has to be one of the easiest changes in outboard repair history (except for the ones on my trim/tilt - those the genius engineers located where you can't remove them without first removing other things!!).

Anyway - it took about 20 minutes start to finish simply because I took the time to remove some green gradu from the electrical connections/wires with a brass brush. The engine had lived in saltwater until last year, and the electrical components (wires, connections, etc) are showing it. I took the time to remove this corrosion and apply some lithium grease to protect them from further degradation.

Thanks again for the help.


Binkie posted 08-23-2005 03:56 PM ET (US)     Profile for Binkie  Send Email to Binkie     
I don`t usually come to this area, as I don`t know much about electrical problems, but I had the exact same problem with my Ford Bronko years ago. I turned the key off and it was still running. I gave the solonoid a whack with a hammer and everything stopped. I replaced it and never had anymore trouble. Then another time I had an outboard that when I turned the key, nothing happened. I jumped the two sides of the solonoid with a pair of pliers and it started. Same remedy. I think the solonoid is a magical part, and when the magic is gone your out of luck.
Buckda posted 08-23-2005 04:02 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Agreed...and for $18.75 - this is a part that should probably make its way into anybody's spare part bin, along with extra spark plugs, fuses, etc.


kingfish posted 08-23-2005 04:03 PM ET (US)     Profile for kingfish  Send Email to kingfish     
It's like letting the smoke out of an electrical part - they have just so much smoke in them, and when you let the smoke out, the part is done for...
Backlash posted 08-23-2005 05:31 PM ET (US)     Profile for Backlash  Send Email to Backlash     

"Anyway - it took about 20 minutes start to finish simply because I took the time to remove some green gradu from the electrical connections/wires with a brass brush..."

Get some [i]Corrosion Block[/] and spray it on any and all corroded electrical connections. The corrosion will simply drip off leaving a clear protective film to help prevent further corrosion. This stuff is pricey, but well worth the cost.


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