Stales and won't re-start - 120 Force

BOBPELL

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Problem #1 - no serial number plate so I can't be sure of year. Feel it is approx. 92? Need ID help for sure.

#2 Starts easy, runs great BUT stalls at will. Could run for an hour or 5 minutes. Left me stranded 3 times. Most recently did it in the driveway. By stall I mean stops dead, no sputtering, no warning just dies and won't re-start till next day or later. Was running fine until this started now I will not go out until I'm SURE problem is solved.

Engine is very clean, all connections perfect, rebuilt about 5 years ago and well taken care of. New plugs
and wires, checked stator and meets specs per manual.
Fuel is not the issue, did every possible test. Fuel pump clean, not water in gas, bulb ok, carbs removed and cleaned, floats ok.

Thank in advance for your help!!!!
 

OBJ

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Re: Stales and won't re-start - 120 Force

Bob....next time check for spark at each hole when it stalls. If no spark, may be heat related to an ignition module. I am not real familiar with the force ignition but it does sound heat related.

Or possibly a kill wire is going to ground. Does the rig have tilt and trim and does it make any difference where the engine is trimed when it stalls?
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

I'm assuming the tilt portion of your answer has to do with the gas level it the carb bowel. Good point, I never thought of that, but engine was always level or close to as possible.

Will check each plug for spark - previously just checked 1 (after stalling) and it was ok.

Good stuff - thanks -
 

OBJ

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Re: Stales and won't re-start - 120 Force

You may try this....carry some premix in a spray bottle with you. When it stalls, spray some fuel right into the carb throats and see if it tries to start on that. May point in the right direction to go.
 

eurolarva

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Re: Stales and won't re-start - 120 Force

You mentioned it runs good and for no reason kills and will not start. Are you sure motor is not overheating. When a motor overheats it will not restart usually till after it has cooled down. Have you checked the impeller?
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

That was my very first thought so I changed it first thing.
I forgot to mention it earlier. Reasonably good flow, runs cool.

This is baffling, I took apart EVERY wire connection, cleaned them even if they did'nt need it (none did, very clean.)

I love this boat but it is very unsettling wondering if I'll need to be towed back YET AGAIN.

I must solve the problem for sure!

Thanks for your help - keep the ideas coming
 

roscoe

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Re: Stales and won't re-start - 120 Force

Ok, a few thoughts.

Closely examine the wires up under the flywheel, the ones connected to the stator and trigger. If one has broken insulation, it may ground out the ignition.
If you can, remove the flywheel to perform a closer inspection.

When you go to start it the next day.... does it always start right up, as if nothing was wrong? Or do you sometimes still have a difficult time starting it?

Have you removed the spark plugs after one it its "kill" incidents?
What did the plugs look like?

Were they a little wet (normal), or were they heavily coated with fuel?

Your first job is to determine if it is an ignition/spark problem, or if it is a fuel system problem.


Are your ignition coils blue or black?
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

1. Wires under flywheel - perfect, stator looks fairly new

2. Always starts easily

3. Plugs look normal, yes, slightly wet

4. Coils are blue

That's why this is so confusing - a number of people have begun scratching their heads over this.
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

Thank you for your help - I'm sure with the wealth of knowledge here we will solve the problem
 

roscoe

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Re: Stales and won't re-start - 120 Force

Your motor is either a 1990 or a 1991a, b, or c model.
You have the prestolite ignition (blue coils and blue cd modules).

Starting with the 1991D model, they had black coils and a switchbox.
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

I appreciate your help on that - is this a good thing or a bad thing?
 

roscoe

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Re: Stales and won't re-start - 120 Force

BOBPELL said:
-- is this a good thing or a bad thing?

Neither good nor bad.
Just trying to id the system so we can possibly figure out what is wrong with it.

Well, a little bit bad. The switchbox was a bit more reliable than the cd modules.
If you ever need to replace any of the ignition components, get aftermarket parts, as the Mercury factory parts are outrageously overpriced.
 

roscoe

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Re: Stales and won't re-start - 120 Force

You said it has new plug wires.
Were these put on before or after the problem arose?
Were these wire core wires, or automotive type wires?
Automotive wires have way too much resistance for that ignition system, and my be causing you troubles. Although usually there are symptoms in addition to stalling.
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

I put them on before the problem started.
I don't know what type they are as they were given to me.

I can test them - what should the resistance be?

I do know that due to their short length, they are not even close to anything they could arc to.

Thank you
 

roscoe

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Re: Stales and won't re-start - 120 Force

Sorry, can't give you a number, just know they have to be low resistance wire core.
Not the high resistance carbon ones that they use in modern autos.
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

Here is an update -

I discovered I have the wrong spark plugs, so that will be corrected.

I also learned that the resistance of wires for mine is
7000 ohm/ft. Probably the same for most early 90's outboards.

I hope info helps others.
 

Frank Acampora

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Re: Stales and won't re-start - 120 Force

You may have a heat short in your stator. The stator has two separate windings: One to charge the battery and one to charge the CD modules. Next time it stalls, as above, check for spark . If you have no spark on all cylinders, Check to see if you have about 200-250 volts to the CD boxes while cranking. If not, check the engine while cool and cranking .if voltage is proper, heat from the engine is shorting out the stator (bad insulation on wires; happens to air cooled lawn mowers all the time.) Replace stator. Very expensive. If you have spark to any cylinder when it stalls, the problem is not the stator. This assumes that you have checked all wires and found none broken or frayed, and all grounds are solid. You may also have bad triggers but it is unlikely that all would be bad. but check them while cranking, they should put out about 1/2 volt signal
 

BOBPELL

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Re: Stales and won't re-start - 120 Force

Frank -

Thanks for the help, I will do all you suggested.

I guess the frustrating part is that the problem is intermittent.

THANX AGAIN
 

Frank Acampora

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Re: Stales and won't re-start - 120 Force

You know, last night in bed I was thinking more on this problem and I remembered something: In the old days when cars had points ignition, there was always a condenser (capacitor) to absorb surges and keep the points from arcing and burning. A bad capacitor would fail and stall the car. After a while, the car would start and run for a while then stall again.
Your CD boxes are Capacitor Discharge units. The stator charges the capacitors and transistors are signaled by the triggers to dump the charges into the respective coils. To stop the engine you short the capacitors to ground.
There is a lot of power going through these boxes and power equals heat. Additionally, these boxes are potted which means they retain the heat. The normal mode of capacitor failure is the dialectric breaks down under heat and the capacitor shorts out. When it cools--in your case could be hours or day- the capacitor will function again until it heats and fails. Presto! Intermittant problem. And it will not happen at regular intervals or specific speeds. And at low cranking speeds when the stator is not putting out maximum voltage, the capacitor may function.

You need to find a mechanic with the proper "Merc-o-meter" LOL to test your units. Lacking that, If you have a REALLY good friend with a couple of good units to use as testers on your engine, try to borrow them.
 
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