OMC 4.3l V6 was running good, now it wont

[krustyCrab]

Hello All,

I just encountered a problem with my motor that I cant seem to figure out.

Specs: 1986 4.3l V6, Stringer, Rochester 2gc carb

I picked up this boat a few weeks ago and after some troubleshooting I was able to get the motor started and running like a champ. The issue there was timing which once corrected was no longer an issue. I started and ran the motor several times, put it in gear and verified sterndrive was functioning, All was well at this point.

I didnt run the motor for 3 days while I fixed some other non-mechanical issues with it. In that three days the only work on or near the engine was re-doing the exhaust, i was having some leaking and i buttoned it up with new hoses etc. I also re-wired all of the lights in the boat, grounded it all and just familiarized myself with the electrical.

So yesterday I decided to fire up the engine to verify all was good in preperation of splashing it this morning. Well no luck, initially it sounded like I wasnt drawing enough power, perhaps I made some mistakes with my wiring, so everything I did I ripped apart and low and behold the engine started cranking with full power like I expected. However it would not stay running, what I mean by that is if i keep the key turned the engine sounds like it was running, but as soon as i let go of the key nothing.

I tried absolutly everything I could think of today, I retraced all of the electrical looking for any possible shorts or improper grounding, I replaced the ignition, replaced the fuel pump, verified i have fuel to the carb(when i throttle down I see my primary squirts), I pulled the coil wire at the distributor and verified that I have spark, I pulled a plug wire on cylinder 1 and verified spark, readjusted the choke, verified oil was clean and at the appropriate levels, verified power to my assist solenoid.

I am at a complete loss at this point, I dont see a kill switch anywhere, my wiring all looks good to the gauges, im getting enough juice, I am fairly certain im getting fuel, I know im getting spark. I had this engine running three days ago and didnt do anything that could have caused it to stop running.

Any help offered would be appreciated.

 

[glenn property of pam]

most probably a bad resistor wire going to the coil. locate the resistor wire that goes to the coil and test it with a ohm meter or test the + connection at the coil it should be around 10v when the key is switched on but not being cranked. There is a second wire to the coil that will feed the coil 12v while the engine is being cranked which is why it can run while the starter is engaged.

 

[southkogs]

Have you tried starting the engine without the drive attached? The upper gear case in a Stringer drive is always turnin'. If for some reason you have an issue with that upper seizing up, it can stall the engine out.

 

[krustyCrab]

I will check the resistor wire from the coil tomorrow morning and let you know how that goes. All attempts to start the engine are while in neutral, that should alleviate the upper gearcase turning, right? I was able to test the sterndrive with no issue, so I would also assume that it wouldnt be seized if that were the case. I am correct in that assumption.

 

[bruceb58]

With the ignition in the on position, what voltage do you measure at the coil? Should be 12.5V with points open or around 9Vwith points closed. The reason it sounds like it starts while cranking is that the coil is fed directly form the starter solenoid while cranking.

 

[krustyCrab]

Ok, so heres something interesting. I went and purchased a multimeter a short while ago, in hopes of verifying the actual voltage, ohms, resistance. Just as an FYI this is the first time I have ever used a multimeter, wasnt to hard to figure out, if in fact I did it correctly.

Anyway, I hooked up the battery and put the ignition into the on position. I wasnt sure how to go about testing so i pressed the black pointer to a known good ground and put the red one on the coil where the resistor wire and yellow wire are attached. The readings i recieved were all over the map when it came to ohms... So I decided to test the battery voltage directly, black on neg, red on positive... I registered 12v. So with that logic I kept the black to the neg battery terminal and then touched the coil with the red, well interestingly enough i read 3.5v, so just for testing purposes I touched the other side of the coil, it read like 125v which i thought was very odd.

While I cant confirm I tested correctly, I can say this... The resistor wire from the alternator to the coil was freaking hot as heck, I had only plugged in the battery about 3-4 minutes prior to the test... So im thinking that I have a definite electrical problem, but where and why... The only suspect change to the electrical was done yesterday when i replaced the ignition, I wired the small yellow cable to the starter position on the ignition, the fat red wire to battery, and the small purple to acc. Did I do that wrong? Could the fact that the resistor wire get so hot mean I have a short, bad ground etc...

 

[krustyCrab]

I should also mention that I touched the black pointer to one side of the coil and the red to the other, set the multimeter to ohms, from memory I think the reading was 1.2-1.4 but it was bouncing around.

 

[bruceb58]

I should also mention that I touched the black pointer to one side of the coil and the red to the other, set the multimeter to ohms, from memory I think the reading was 1.2-1.4 but it was bouncing around.

Don't measure to the ground side of the coil. Measure to ground of the engine.

 

[southkogs]

All attempts to start the engine are while in neutral, that should alleviate the upper gearcase turning, right?

Sounding like a non-issue, but for future reference your upper gear case is always moving - even in neutral. It's your lower gear case that will go into neutral.

I was able to test the sterndrive with no issue, so I would also assume that it wouldnt be seized if that were the case. I am correct in that assumption.

If the sterndrive is moving freely (and you've tested that), then it's probably okay. That was a long shot, but one that some folks will skip.

 

[krustyCrab]

Ok, so heres something interesting. I went and purchased a multimeter a short while ago, in hopes of verifying the actual voltage, ohms, resistance. Just as an FYI this is the first time I have ever used a multimeter, wasnt to hard to figure out, if in fact I did it correctly.

Anyway, I hooked up the battery and put the ignition into the on position. I wasnt sure how to go about testing so i pressed the black pointer to a known good ground and put the red one on the coil where the resistor wire and yellow wire are attached. The readings i recieved were all over the map when it came to ohms... So I decided to test the battery voltage directly, black on neg, red on positive... I registered 12v. So with that logic I kept the black to the neg battery terminal and then touched the coil with the red, well interestingly enough i read 3.5v, so just for testing purposes I touched the other side of the coil, it read like 125v which i thought was very odd.

While I cant confirm I tested correctly, I can say this... The resistor wire from the alternator to the coil was freaking hot as heck, I had only plugged in the battery about 3-4 minutes prior to the test... So im thinking that I have a definite electrical problem, but where and why... The only suspect change to the electrical was done yesterday when i replaced the ignition, I wired the small yellow cable to the starter position on the ignition, the fat red wire to battery, and the small purple to acc. Did I do that wrong? Could the fact that the resistor wire get so hot mean I have a short, bad ground etc...

I should have also mentioned, that with the ignition in the on position, I used my test light to verify power at the positive leg of the coil, the light was extremely dim. Dim to the point where you could just see the filament glow faintly.

 

[bruceb58]

I should have also mentioned, that with the ignition in the on position, I used my test light to verify power at the positive leg of the coil, the light was extremely dim. Dim to the point where you could just see the filament glow faintly.

Use your meter for these measurements.

 

[krustyCrab]

Will do sir, I will post the complete results this evening. Unfortunately im at work right now, gotta pay for this boat somehow...LOL

 

[Heywire77]

I had the same problem on a boat before and it was the kill switch because it would start and run as long as I held the key and as soon as I let off the kill it would kill it and it was a and kill switch l get a wiring diagram and check voltage is were your suppose to have it check kill switch make sure you have your meter set to the right voltage when checking everything also sounds like you had it set to ac voltage .

 

[krustyCrab]

I verified the meter was set on DC, I once again tested voltage to battery black on neg red on pos, reading was 12.4v I then kept the ground on the neg terminal and tested the positive side of the coil, reading was 3.4v.

So I traced the yellow wire from the coil to the starter, I read 3.4v at the starter as well, but if i test the big post on the starter I have 12v... Does this mean the starter is bad?

I have no idea where a kill switch would be if there is in fact one, i traced out all of the wiring, consulted the manual. I dont know what else to look for with regartd to that.

 

[krustyCrab]

I verified the meter was set on DC, I once again tested voltage to battery black on neg red on pos, reading was 12.4v I then kept the ground on the neg terminal and tested the positive side of the coil, reading was 3.4v.

So I traced the yellow wire from the coil to the starter, I read 3.4v at the starter as well, but if i test the big post on the starter I have 12v... Does this mean the starter is bad?

I have no idea where a kill switch would be if there is in fact one, i traced out all of the wiring, consulted the manual. I dont know what else to look for with regartd to that.

Ok I tested further, I removed the wire between the coil and starter, I still register 3.4v at the coil... Guess my theory on the starter is out the window... Not sure what else i can look for.

 

[PaJon]

I verified the meter was set on DC, I once again tested voltage to battery black on neg red on pos, reading was 12.4v I then kept the ground on the neg terminal and tested the positive side of the coil, reading was 3.4v.

So I traced the yellow wire from the coil to the starter, I read 3.4v at the starter as well, but if i test the big post on the starter I have 12v... Does this mean the starter is bad?

I have no idea where a kill switch would be if there is in fact one, i traced out all of the wiring, consulted the manual. I dont know what else to look for with regartd to that.

3.4V is not enough, it should be 9VDC with the key in the on position. Disconnect the negative side on the battery. Switch the meter to ohms and measure the resistance of the resistance wire that's connected to the plus side of the coil ( I think it's a yellow wire ). Also disconnect all wires on the coil and measure the resistance between the plus and negative side of the coil.

One other thing to try before trying to start it again.... remove the grey wires from the negative side of the coil. A bad tach can cause odd ignition problems.

 

[krustyCrab]

I finally got it started, after looking at all the wiring, I figured hey a new coil is only 35 bucks, picked it up, installed, and she started right up with no other corrections needed. I am going to test the voltage at the coil again tomorrow to verify the setting. I will post the results here. Thank you everyone for your feedback and assistance thus far.

 

[bruceb58]

It is normal to measure the same voltage at the coil positive to the terminal at the starter solenoid where you measured.

 

[krustyCrab]

It is normal to measure the same voltage at the coil positive to the terminal at the starter solenoid where you measured.

I realized that shortly after I posted that comment, and thought to myself "wow the guys on iboats are going to think im a dummy LOL" I assure you im really not, I just dont think things through all of the time...