1988 4.3 OMC Cobra 4bbl No Spark from coil

[lasko1]

Not getting spark from coil.

Background: Took the boat out for the 1st time this year (in Michigan). Started it up on the muffs in the driveway and she fired right up. Went fishing and the boat started and ran well at 3/4 throttle on the way out. Shut the boat off and trolled with electric trolling motor. Started boat back up with ease several different times. Fired it up the last time to head in, and after running about a mile at 1/2 to 3/4 throttle, the boat just DIED. Acted like I just shut the key off. Engine would roll over fine, but would not fire.

Got towed in and got home. Pulled a plug wire off #1 cylinder and put in a spare plug and grounded it to the block. Rolled engine over and NO spark. Put plug wire back on #1 plug and pulled the coil wire off distributer cap and set it within 1/4" of exhaust manifold...rolled engine over...still no spark. Re-Installed coil wire to dist. cap.

I Used a multimeter and I do have 12.3 volts at battery, ~11 volts on positive side of coil when key is in the on/run position. I also have ~11 volts on (-) side of coil with key on. Is there supposed to be that high of voltage on the (-) side of the coil with just the key in the on/run position? It consistently measured ~11volts on the (-) side even after I rolled the engine over a few different times.

I have 1.5 ohms when going from (+) side of coil to (-) side of coil. I Pulled the wire off top of coil and I have 9.6 ohms when going from (+) side of coil to inside the top of the coil where the distributor wire plugs in. I also have the same 9.6 ohms when going from the (-) side of coil to the inside of the top of the coil.

I have not pulled distributor cap yet. (Points & condenser are 2 yrs old)

Thoughts? Bad points? Failed Condenser? Something else tied to the (-) side of the coil shorted out?

On the (-) side of the coil is 1 black wire and 2 gray wires. Black wire goes to dist. cap. Not sure where the 2 gray wires go.

Like I said, the boat just died while on plane. Wondering what would cause the immediate loss of voltage.

 

[Scott Danforth]

negative side of the coil is pulsed to ground by the points. most likely either your points are not adjusted right, the condernser went bad, or they arced. this is most likely your issue.

with +12 volts to the + side of the coil, all you need to do to get spark is ground the - side, then remove it from ground.

it is almost never the coil. (ok, 99.99% of the time its never the coil)

grey wires are tach

if your tach went bad, it would be grounding out the - side. worst case, disconnect the grey wires and try.

 

[Bondo]

I Used a multimeter and I do have 12.3 volts at battery, ~11 volts on positive side of coil when key is in the on/run position. I also have ~11 volts on (-) side of coil with key on. Is there supposed to be that high of voltage on the (-) side of the coil with just the key in the on/run position?

Ayuh,.... 11 volts is abit low,.... clean the battery cables to shiny clean metal, both ends of both cables,.....

The coil checks that way til the ignition grounds it to fire the coil,....

I have not pulled distributor cap yet. (Points & condenser are 2 yrs old)
Thoughts? Bad points? Failed Condenser? Something else tied to the (-) side of the coil shorted out?
On the (-) side of the coil is 1 black wire and 2 gray wires. Black wire goes to dist. cap. Not sure where the 2 gray wires go.

The Points is the 1st place to look,.... high maintenance part, need cleanin' 'n settin', Annually,...
The grey wire feeds the tach,....

 

[lasko1]

Thank you both for your responses.

Question: Do both gray wires from the (-) side of my coil go to the tach? Or does just 1 gray wire go to the tach and the other go to something else?

1st troubleshooting effort will be to do as Scott suggested and remove both gray wires from (-) side of coil and see if I get spark. If I get spark, then I have to figure out which of the gray wires is shorted out by only connecting 1 gray wire at a time.

If I don't get spark, then its either points or condenser and I plan to change both out anyways.

Lastly, I had already cleaned my battery connections to a shiny metal on both ends of the cable. I also cleaned the 2 other smaller ring terminals that attach to the starter solenoid where the positive battery cable attaches. I will remove, clean, and reinstall all the terminals that attach to the (+) and (-) of the coil. I have ~12.3v at battery (slightly discharged from rolling engine over after loss of power). Hopefully cleaning the terminals on the (+) side of coil will give me the same voltage as the battery.

One other question: There is a purple wire with gray stripe (resistor wire??) that attaches from a small stud of the starter solenoid and goes to the (+) side of the coil. Could this reduce the voltage measured on the (+) side of the coil? I will clean both ends of this wire also.

I will give all this a shot and report back with my findings.

 

[Bondo]

Question: Do both gray wires from the (-) side of my coil go to the tach? Or does just 1 gray wire go to the tach and the other go to something else?

Ayuh,..... 1 has to go to the shift switch, which grounds the ignition for a second, to allow the drive to come outa gear, when in the water,....

Lastly, I had already cleaned my battery connections to a shiny metal on both ends of the cable.

But ya didn't do the Grounds(-),.....

One other question: There is a purple wire with gray stripe (resistor wire??) that attaches from a small stud of the starter solenoid and goes to the (+) side of the coil.

That wire supplies battery voltage to the ignition, Only while the starter is engaged,....

 

[Scott Danforth]

^+1....What he said.

 

[lasko1]

Ok fellas, one step closer. Last night I disconnected the gray wires from the (-) side of my coil and left the black wire connected. (I was surprised to see the gray wires were actually merged together into 1 ring terminal).

I pulled the coil wire off the dist. cap and layed it 1/4" from my exhaust riser. I had 11.3v on the (+) side of coil at this time. I rolled the engine over and still no spark out of the coil wire. I believe this eliminates the tach or ESA from being the issue. This afternoon I am going to pick up a new points kit which includes the condenser and new rotor and will install those.

In an effort to get the full 12v on the (+) side of the coil, I had cleaned all my associated terminals to a shiny finish and rechecked my voltage going to the (+) side of my coil. Uh oh, it now only read 1.2volts. After rechecking all the terminations I had cleaned, I finally found the main harness plug is the culprit of the voltage issue. This is the one with the worm-gear clamp holding the 1.5" male and female connectors together. I wiggled the connectors and my voltage jumped all over the place. I then cleaned the male prongs and female sides, opened the male prongs just a tad, and plugged it back in. Viola, I'm now up to 11.9volts.

Now I have a question about this plug connection. How far together should these connectors go? In other words, should the side with the female connections go all the way in and cover the entire length of the male prongs? If so, I have an issue. Mine is only going in ~1/4". It has been this way for years as far as I can tell by the indents left by the worm-gear clamp and the indents from the metal connection holders. The worm-gear clamp really isn't holding much at this point.

The worm-gear clamp must have been tightened without covering both ends of the plug connections and it deformed the rubber of the prong side connector. It made the "internal" lip higher on the rubber prong end connector and I believe that's what's stopping the other connector from sliding in further.

I'm not sure how to upload pictures at this time so I hope the links below work. The picture links below are NOT my actual connectors. I doctored them up to show approximately how far my connector goes in. The red line in the 1st pic is about how far my connecter goes in and the blue line would represent all the way in and covering the entire length of the prongs. The red arrow in the 2nd picture is the internal lip I was talking about, and the lip on my connector is much higher due to the clamp pinching in.

Thoughts?

https://www.iboats.com/photo/51497?row=1
https://www.iboats.com/photo/51496?row=2

 

[Bondo]

Ayuh,.... That's yer problem,..... The plug should be bottomed out,....

When ever I'm tryin' to crowd together Rubber pieces that don't what to go together,.....
I grab my spraycan of Quicksilver Power Tune, 'n give the parts a tiny, tiny spray, then stuff 'em together,....
So far, it's never failed,.....

 

[lasko1]

Ok, thanks Bondo. I'm takin the rest of the day off and heading to the local marine store to get my points, condenser, and rotor tune up kit and will see if they have any tof the Quicksilver Power Tune.

Will respond back with results after everything is installed.

 

[lasko1]

UPDATE: Got the new points, condenser, and rotor this past Friday. Removed dist. cap (which obviously should've been my first troubleshooting effort) and immediately found the thin copper connector strip that goes from point set to the dist. plate mounting screw to be fatigued and broken. Replaced it and set point gap to .018 for a starting point. Checked and got spark from coil wire to ground. Problem solved.

Grounded coil wire, rolled engine over, and checked the dwell and it was at 34. Reset point gap to .017 and finally to .016 to achieve 38 dwell. Just need to set timing now. Will be aiming for 6 deg BTDC. Waiting for weather to remain above freezing so I don't have to re-winterize.

While double checking my connections after putting everything back together, I re-checked my voltage on the (+) side of my coil. To my surprise, I was only getting 6.0 volts. I removed both wires from (+) side of coil and measured 11.8volts on wire coming from big lug of starter solenoid (NOT the purple resistor wire). Re-connected both wires to (+) side of coil and voltage immediately dropped to 6.0 volts again. By hand, I slowly rotated engine over to move the distributor shaft and points and watched volt meter come up to 11.8 volts and then drop back down to 6.0 volts as I kept rotating engine. I believe the voltage goes up to 11.8 when the points open and then voltage drops back down when points close.

Question: Does the 6.0 volts sound correct?

 

[Maclin]

What do you have the meter's negative connected to? The 6 sounds a little low, but then the 11.8 seems low also. When the resistor is in play there should be around 9v. As you suspect, depends on if the points are open or closed while reading the meter.

I would do the measurements again with coil wires disconnected. Meter negative lead on good engine/batt ground, and positive lead on the coil wires together, with key on, should see about 9v in a ballasted circuit. Voltage would jump to 12v when/if key moved to Start.

 

[lasko1]

When checking for voltage on teh (+) side of the coil, the negative lead was grounded to the spark arrestor stud initially. I thought the 6v reading was low also, so I moved the negative to a couple different grounds and got the same 6v reading.

My battery was slightly discharged at 12.3volts from cranking and not being re-charged. I checked voltage at the fuse block under the dash and I get 12.2 volts. I checked voltage at the main wiring harness 1.5" plug connectors female side and still have 12.2v. When I plug the main harness connections back together, I only have 11.8v on the (+) side of the coil. I will

In posts #7 and #8 above, I talk about the 1.5" main harnass connectors and how they don't slide all the way into each other and I know I have some voltage loss at that connection. I talked to the local marine repair shop and they said to be gentle with those main harnass connectors because they're not available any longer and it'd be a REAL pain in the butt to have to replace them.

Its still cold here in Michigan and the rubber on the prong side connector (seen in link below) is stiff and I thought that was preventing the female side connector from going all the way onto the prongs. Mechanic suggested to warm up the external rubber on the prong side connector (that the worm-gear goes on) and apply some WD40 to the side that slides onto the prongs. In post #8 above, Bondo suggested using the QuickSilver Power Tune, but they didn't have any of that on hand. I tried all of that and the connections still are not bottoming out. I don't know exactly what's keeping them apart, but they just don't want to go all the way together. I am thinking about warming up the connections and using some dialectric grease to see if the one connection will then slip all the way over the prongs of the other connector. The mechanic said he has seen this issue before and to be very careful with the connectors and especially not to overtighten the worm-gear clamp.

https://www.iboats.com/photo/51496?row=2

 

[lasko1]

Last night I applied the dialectric grease and warmed up the connections and after a few tries, I got them to go together a lot further. They didn't go 100% together, but they are at least 75% together. The thing is, it didn't help my voltage increase at all, so 11.8 - 11.9 volts is the best I get on the (+) side of my coil when the points are open.

Its supposed to warm up here, so the next thing I need to do is put the muffs on, fire up the engine, and set the timing.

Will report back when that is complete.

 

[lasko1]

Was 70° out today and I put the muffs on. Engine fired right up at 38 dwell. I measured the voltage on the positive side of the coil while the engine was running and I had anywhere from 9 to 10volts. I set the timing to 6° BTDC. Everything seems to work fine. So, to close out this post, my main issue was a broken connection from the points to the distributor plate.
Drained water and re-winterized the engine and exhaust manifolds and I am now waiting for a decent day to get out fishing