140 mercruiser missing after it gets warm

[dubs283]

Re: 140 mercruiser missing after it gets warm

bright blue thick spark = good, orange thin dim spark = bad

there should be roughly 9 volts at the coil primary with the key on, it may jump to around 10 while running

 

[wrench 3]

Re: 140 mercruiser missing after it gets warm

It will only drop to the 9 volts (may be 8) when the points are closed.
Could you post a picture of the ground wire you re-connected. There's normally no extra grounds on the trim pump.

 

[AKPilotnboatman]

Re: 140 mercruiser missing after it gets warm

I had similar issues with my 1968 Penn Yan with the 160 in it. I was not getting spark or start, then I jiggled a few things around, shocking myself in the process, then pow! Started right up. Mine does have the external ballast resistor though. Then again I still have a couple wires hanging out unconnected and I really cant figure out where they go... odd. Anyway, good luck! How is your overall system voltage when running? or, when it was running>?

 

[dubs283]

Re: 140 mercruiser missing after it gets warm

It will only drop to the 9 volts (may be 8) when the points are closed.

no, it will always be around 9 volts - due to the resistor wire, the only time you will see more is during starting

 

[splatter]

Re: 140 mercruiser missing after it gets warm

I got it started after just a few minutes ( I had the distributor cap hooked up wrong . ):facepalm: Then I took it to the lake . Just like always 30 minutes in and bam spit and sputter so bad it will barely run . So I changed all the plugs with new ones I bought today ran good for 5 minutes then same thing . So I disconnected the grey tach wire from the negative side of the coil and the symptoms completely changed . With the wire off the boat runs rough but better than when it acting up . (I can run about 25MPH WOT with the wire off . When its acting up I can't get to 5MPH or open the throttle to WOT.When the boat is running like it should ( first 30 minutes ) it will do 40 mph. )
So what I'm saying is with the tach unhooked it runs crappy but better.


also I checked the voltage at the positive terminal on the coil . Switch on= 5vdc . running =12vdc . switch on with negative terminal open =12v . It only drops to 5V if I have the ground hooked up on the negative terminal.

At this point I have no clue . I can't figure out what the tach wire could have to do with anything .

 

[dubs283]

Re: 140 mercruiser missing after it gets warm

sounds as if the resistor wire has an issue, you should see roughly 9 volts with the key on and sllightly higher with engine running - 12 volts running is too high and causing the points to overheat/burn prematurely

the tach gets it signal from the coil, a faulty tach can cause a no spark issue

the negative side of the coil has the ground controlled through the points, i.e. points open path to ground is through the tower to dist cap, points closed path to ground is through points and back to battery through engine ground

 

[MikDee]

Re: 140 mercruiser missing after it gets warm

Replaced the condenser and no change . I also set the gap on the points again,checked the plugs and the plug gaps before I took it out . Also checked all the connections and every thing looks good . I did notice the points have a hole in the center of the stationary side . Is this normal ? I looks like it was made that way . I didn't notice it last season when I put them on but I don't remember points being like that in the past .

Any way I'm thinking about putting a pertronix electronic ignition on it. At least that would eliminate 2 componets in the chain .Then I though I would change the plugs ,wires , distributor cap and rotor button again . I hate to do it since they are all new but something some where is breaking down and if I do all that I will basically have a new ignition system.

Also I should add . I just changed the outdrive before I put the boat in the water this year . I can't imagine how that could affect anything but I though I should throw that out there .

Only the better brands of points have a hole in the middle, to keep them cool., plus a nice plating job, & a beefy return spring.

 

[MikDee]

Re: 140 mercruiser missing after it gets warm

So what I'm saying is with the tach unhooked it runs crappy but better.


also I checked the voltage at the positive terminal on the coil . Switch on= 5vdc . running =12vdc . switch on with negative terminal open =12v . It only drops to 5V if I have the ground hooked up on the negative terminal.

At this point I have no clue . I can't figure out what the tach wire could have to do with anything .

WAIT!, You should only have ONE wire to the Dist, coming off the Coil Neg - (It acts as a ground), Plus the gray tach wire on coil Neg.

Then you should have 12volts going into the coil Plus + side, ONLY DURING cranking/starting, then becomes a Dead wire (the starter solenoids job) Next, under 9volts for RUNNING from the Resistor wire to the Plus + side. That's the voltage your coil should run at, and you should have a Non-Resistor coil Stock! (std. equip.)

 

[splatter]

Re: 140 mercruiser missing after it gets warm

sounds as if the resistor wire has an issue, you should see roughly 9 volts with the key on and sllightly higher with engine running - 12 volts running is too high and causing the points to overheat/burn prematurely

the tach gets it signal from the coil, a faulty tach can cause a no spark issue

the negative side of the coil has the ground controlled through the points, i.e. points open path to ground is through the tower to dist cap, points closed path to ground is through points and back to battery through engine ground

I'm going to pick up a resistor wire on the way home . Now I have another question for you. Where does the other end of the resistor wire hook up ? I have 2 wires on the + side of my coil ,one is the purple with the yellow stripe that goes to the starter and the other is white . I have no idea where the white wire goes but I suspect it goes to the shift interrupt switch .Every thing I read says there should be a purple wire that is the resistor wire , there isn't. my manual doesn't have a wiring diagram and the diagrams I can find on the net are not very good .
Thanks

 

[MikDee]

Re: 140 mercruiser missing after it gets warm

WAIT!, You should only have ONE wire to the Dist, coming off the Coil Neg - (It acts as a ground), Plus the gray tach wire on coil Neg.

Then you should have 12volts going into the coil Plus + side, ONLY DURING cranking/starting, then becomes a Dead wire (the starter solenoids job) Next, under 9volts for RUNNING from the Resistor wire to the Plus + side. That's the voltage your coil should run at, and you should have a Non-Resistor coil Stock! (std. equip.)

Okay, here's your Fix:

The starter solenoid small terminal on the right saying "S" is for start 12volts Pos + it should only be powered during start, to give you full 12V. for starting/cranking, then it goes dead during Run! and your Resistor wire 9volts (or whatever?) takes over to save your points, & Run your boat! That's it, you have to determine which is your resistor wire, & which is full power?

I'm sure one of the colored wires you have is the resistor, & one is full power. Check the wire at the solenoid that it's on the right terminal marked "S", if so it should be dead with your ignition switch on "Run", and a full 12V on Start/Crank. If not your solenoid is wired wrong, or bad!

I'm guessing your white wire is the resistor wire, and only powered in the Run mode of your ignition switch.

The diagrams I posted, are generic (so wire colors don't match yours) but, you should understand how it all works now.

By the way, the white wire probably comes FROM your shift switch, which is powered till you shift out of gear, then it's momentarily dead till you get thru your shift, okay?

 

[wrench 3]

Re: 140 mercruiser missing after it gets warm

no, it will always be around 9 volts - due to the resistor wire, the only time you will see more is during starting

According to ohms law you get a voltage drop across a resister proportional to the currant flow. With the points open you get no flow, so no voltage drop.

 

[wrench 3]

Re: 140 mercruiser missing after it gets warm

You shouldn't have that much voltage when it's running. The only reason I can think of is if the points aren't staying closed long enough. How is the dwell?

 

[splatter]

Re: 140 mercruiser missing after it gets warm

Okay, here's your Fix:

The starter solenoid small terminal on the right saying "S" is for start 12volts Pos + it should only be powered during start, to give you full 12V. for starting/cranking, then it goes dead during Run! and your Resistor wire 9volts (or whatever?) takes over to save your points, & Run your boat! That's it, you have to determine which is your resistor wire, & which is full power?

I'm sure one of the colored wires you have is the resistor, & one is full power. Check the wire at the solenoid that it's on the right terminal marked "S", if so it should be dead with your ignition switch on "Run", and a full 12V on Start/Crank. If not your solenoid is wired wrong, or bad!

I'm guessing your white wire is the resistor wire, and only powered in the Run mode of your ignition switch.

The diagrams I posted, are generic (so wire colors don't match yours) but, you should understand how it all works now.

By the way, the white wire probably comes FROM your shift switch, which is powered till you shift out of gear, then it's momentarily dead till you get thru your shift, okay?

ok thanks ,My purple yellow is wired to that terminal on the solenoid .I'll take some reading and make sure the solenoid is good .
I'll post back tomorrow with the results .

 

[MikDee]

Re: 140 mercruiser missing after it gets warm

ok thanks ,My purple yellow is wired to that terminal on the solenoid .I'll take some reading and make sure the solenoid is good .
I'll post back tomorrow with the results .

If you can separate the wires? Take them off, then check voltage at the Solenoid wire in "ON" or "Run" position of the ign. switch, it should be O volts!

Then check at the Solenoid wire, with the ign. switch at the "Crank/Start" position it should be 12V or battery voltage.

If not, your Solenoid is bad. If all is well here, then there's a different problem.

The Resistor wire, (which probably is not even copper) but white metal should read under 12 volts with the ign. switch at ON/RUN. I'm not sure about crank, if it's powered then?

Also, remember there should only be one wire on the Neg - terminal going to the Distributor,,, plus the gray tach wire. You cannot add another ground wire here, or it will SHORT OUT the whole system! Theoretically you will have NO SPARK!

 

[dubs283]

Re: 140 mercruiser missing after it gets warm

According to ohms law you get a voltage drop across a resister proportional to the currant flow. With the points open you get no flow, so no voltage drop.

i think you're having a hard time understanding how the system works, no one here is referring to the voltage on the negative side of the coil, that is not where you measure the resistor wire voltage - the voltage is measured on the poistive side of the coil, a constant voltage supply from the battery dropped down to roughly 9 volts key on and slightly higher engine running due to alternator output

you would never be able to see the voltage drop at the negative side of the coil with the engine running, the points open/close roughly 20 times a second at idle, no voltmeter can measure that voltage drop

 

[splatter]

Re: 140 mercruiser missing after it gets warm

You shouldn't have that much voltage when it's running. The only reason I can think of is if the points aren't staying closed long enough. How is the dwell?

I don't have a dwell meter . I set the points with a feeler gauge

 

[splatter]

Re: 140 mercruiser missing after it gets warm

If you can separate the wires? Take them off, then check voltage at the Solenoid wire in "ON" or "Run" position of the ign. switch, it should be O volts!

Then check at the Solenoid wire, with the ign. switch at the "Crank/Start" position it should be 12V or battery voltage.

If not, your Solenoid is bad. If all is well here, then there's a different problem.

The Resistor wire, (which probably is not even copper) but white metal should read under 12 volts with the ign. switch at ON/RUN. I'm not sure about crank, if it's powered then?

Also, remember there should only be one wire on the Neg - terminal going to the Distributor,,, plus the gray tach wire. You cannot add another ground wire here, or it will SHORT OUT the whole system! Theoretically you will have NO SPARK!

I separated the wires and the solenoid works as you described . I didn't check the other wire in the on position but I did check it with the engine running and I got 12v . ( I pulled the solenoid wire off while it was running and measured the voltage on the coil post while the resistor wire was still attached .)
I changed the resistor wire and I still have 11.5 to 12 v on the positive side of the coil . this is with the engine idling . It jumps to about 12.5 when reved . I tore open the wiring harness and spliced the new wire in where the old wire was spliced in . I took the readings while I still had the harness open and since I saw it was still high voltage I took a reading where the resistor wire splices in coming off the alternator . I had 12.57 coming straight off the alternator while idling . this seems normal to me . At first I thought that maybe the alternator was putting out to much voltage but that doesn't seem to be the case .

BTW the old resistor wire measures 2.5 ohms the new wire measures 1.5 ohms . I feel like I'm going backwards .

Also there are only 2 wires on the neg post . dist and tach.

i don't have an ammeter so I have no Idea what amperage the alternator is putting out . I guess I could open the ckt and get the current that way, then figure out what size resistor I need to drop the voltage to 9v .

 

[MikDee]

Re: 140 mercruiser missing after it gets warm

I don't have a dwell meter . I set the points with a feeler gauge

That don't matter much now,,, I'm trying to establish a baseline here.

Did you take off the solenoid wire at the coil, and test IT for voltage when in cranking/starting mode, then in Run mode, of the key switch?
and did you happen to test the voltage on the Resistor wire using the same method?

 

[dubs283]

Re: 140 mercruiser missing after it gets warm

that is very strange, especially with the wire's resistance, i guess you could daisy chain the old and new, see if that drops the voltage enough...sounds like your doing everything as you should

 

[MikDee]

Re: 140 mercruiser missing after it gets warm

I separated the wires and the solenoid works as you described . I didn't check the other wire in the on position but I did check it with the engine running and I got 12v . ( I pulled the solenoid wire off while it was running and measured the voltage on the coil post while the resistor wire was still attached .)
I changed the resistor wire and I still have 11.5 to 12 v on the positive side of the coil . this is with the engine idling . It jumps to about 12.5 when reved . I tore open the wiring harness and spliced the new wire in where the old wire was spliced in . I took the readings while I still had the harness open and since I saw it was still high voltage I took a reading where the resistor wire splices in coming off the alternator . I had 12.57 coming straight off the alternator while idling . this seems normal to me . At first I thought that maybe the alternator was putting out to much voltage but that doesn't seem to be the case .

BTW the old resistor wire measures 2.5 ohms the new wire measures 1.5 ohms . I feel like I'm going backwards .

Also there are only 2 wires on the neg post . dist and tach.



i don't have an ammeter so I have no Idea what amperage the alternator is putting out . I guess I could open the ckt and get the current that way, then figure out what size resistor I need to drop the voltage to 9v .

NOooooooooooo! You're making this all too hard!

The Resistor wire comes from the key switch, it is aluminum, or white metal of some type, so it becomes a resistor automatically,,, not delivering the full 12 Volts.

The only thing I can think of, is that someone monkeyed with, and switched the wires on the ignition switch?