140 hp mercruiser starting issues, troubleshooting performed. Lost!

[Motodox]

I just thought of something for you to check.


Does your boat have a tachometer at the helm? If it does, disconnect it. It hooks to the coil - terminal & depending on the year it might be grey or if it's older it could be dark brown like mine.

Those tachs, especially on an older boat, get all jacked up inside & ground out that circuit, essentially becoming a kill switch for your ignition. If I hook my tach up, the engine will start missing & surge for a few seconds & then die. Every time.

Biggjimm I really appreciate all the help too. I should be a ignition wizard by the time I'm done.

As for the tachometer I never thought Of that? I do know when I'm crankin over the tachometer is reading. But still like we discussed I jumped 12v directly to the coil wouldn't that bypass that if it were to be a problem?

 

[Motodox]

I just thought of something for you to check.

Does your boat have a tachometer at the helm? If it does, disconnect it. It hooks to the coil - terminal & depending on the year it might be grey or if it's older it could be dark brown like mine.

Those tachs, especially on an older boat, get all jacked up inside & ground out that circuit, essentially becoming a kill switch for your ignition. If I hook my tach up, the engine will start missing & surge for a few seconds & then die. Every time.

Also, I do have a grey wire on the - side of coil and a black wire which runs to the ignitor. I could of swore the grey wire ran up to the one and green wire which went to the shift interrupt.

So coming from the shift interupt there is a white and green wire if I remember correctly and it runs to a split where two grey wires come out. One goes to - side of coil and the other follows the harness up. Is that the tach wire I assume?

I have the wiring diagram at home so I can just look then I guess. Just at work now thinkin on the issue

 

[biggjimm]

On mine the tach wire & the shift interrupt both hook up to the - coil term with the black wire going to distributor. Yours could tie in with the shift interrupt wire farther back in the harness I suppose. If so just unhook the shift interrupt wire from the coil for testing purposes in the driveway. If the tachometer proved to be the culprit, just cut the wire where it spliced in or unhook it at the tachometer.

If the tachometer is bad & grounding that circuit it doesn't matter where you get the voltage to the coil + side, if the other side is grounded thru the ttachometer it will kill your spark. A bad shift interrupt that was stuck closed would do the same thing. That's what the shift interrupt is designed to do, kill the power to the coil for a split second to take the load off the dog clutch in the lower unit to make shifting out of gear easier. If all is working correctly you hardly notice it if you notice it at all. I don't but some guys say they do.

Just to be sure, you can take all the wires off the coil - except the black wire going to the distributor. And take the wires off the coil + side & just jumper from the battery (if it starts, you'll have to remove the jumper wire to kill the engine though) & this removes everything out of the equation, ignition switch, crank wire from solenoid, resistor wire, tachometer, shift interrupt & everything that could potentially be shorted out or not working. If it starts then hook em back up one at a time until you find the offending circuit. If it doesn't fire & start then it's in the distributor or coil or wires & such. That's how I diagnosed mine & I had 3 separate issues with it.

 

[scamp12]

That thing is made in China . Not reliable at all . On the street or in a boat . I hope they dont sell one for a plane cause u be f d

 

[Motodox]

On mine the tach wire & the shift interrupt both hook up to the - coil term with the black wire going to distributor. Yours could tie in with the shift interrupt wire farther back in the harness I suppose. If so just unhook the shift interrupt wire from the coil for testing purposes in the driveway. If the tachometer proved to be the culprit, just cut the wire where it spliced in or unhook it at the tachometer.

If the tachometer is bad & grounding that circuit it doesn't matter where you get the voltage to the coil + side, if the other side is grounded thru the ttachometer it will kill your spark. A bad shift interrupt that was stuck closed would do the same thing. That's what the shift interrupt is designed to do, kill the power to the coil for a split second to take the load off the dog clutch in the lower unit to make shifting out of gear easier. If all is working correctly you hardly notice it if you notice it at all. I don't but some guys say they do.

Just to be sure, you can take all the wires off the coil - except the black wire going to the distributor. And take the wires off the coil + side & just jumper from the battery (if it starts, you'll have to remove the jumper wire to kill the engine though) & this removes everything out of the equation, ignition switch, crank wire from solenoid, resistor wire, tachometer, shift interrupt & everything that could potentially be shorted out or not working. If it starts then hook em back up one at a time until you find the offending circuit. If it doesn't fire & start then it's in the distributor or coil or wires & such. That's how I diagnosed mine & I had 3 separate issues with it.

SUCH GREAT INFO HERE TO TEST PROCEDURE ON YOUR IGNITION SYSTEM.

also everyone else on this forum Rick has been with me the whole time to with great advice. I thank you all so much. I'll get back with the news hoping parts get here quick !

 

[Motodox]

GREAT NEWS!!!!

My pertronix ignition kit arrived today, purchased off amazon for 140$ that came with the module and the coil. I got the better one this time the flame thrower II which has a coil with 0.6 ohms resistance compared to what I had was the original pertronix flame thrower kit with a coil resistance of 3.0ohms.

So I pulled all the old electronic off and hooked up the new coil and ignitor (module) made sure I filed out a groove in the new cap so it wouldn't pinch the wires. If you haven't been following post I replaced the cap rotor wires and plugs as well. Still had spark at the plugs after doing the tune up and still wouldn't start.

So ya I installed the new kit hooked up everything as it should, gave one pump on the throttle and it fired right up!!! No hesitation at all. And ran beautifully, I couldn't believe it. I was so joyed to have finally got her back up and running after many hours of frustration from diagnosing.

So after I got it fired up I hooked my timing light up to #1 plug wire and it worked perfectly unlike before, so I was defintely getting a very weak spark before. So I checked timing when it was running dialed it back in to 6* BTDC and she's purring like a kitten! Shut her down re wrapped my wiring harness with electrical tape seems how I had it all pulled apart for diagnosing. That was the Hardest part was trying to get a nice wrap on all those wires and to get to look factory, talk about a pain in the butt! So now she's all done and ready for another day on the lake then time to get winterized.

All n all don't over look your electronic ignition if your having troubles starting or running. My boat is an 1986 and it died on the lake after running perfect. I had spark, fuel, compression and timing and it wouldn't start, I had proper voltage to coil with key on and the module tested good and the coil ohms out to 3.0 exactly what it should have. Apparently that didn't mean it was good. I had a weak spark that wouldn't even run a timing light and soon as I replaced with the newer electronic kit from pertronix it fired right up !!

I couldn't be any more happy right now and so relieved. Thank you all for the help I've learned so much and will carry this info on and help my fellow boaters here on out. As stated before I feel like a ignition wizard on the 140hp mercs now . Whoooooohoooooo

 

[Motodox]

Took a quick video here it is
https://vid.me/bfeN

 

[Rick Stephens]

Took a quick video here it is
https://vid.me/bfeN

YEAH BABY!!

That's the ticket. Right on brother. Now time to go boating.

Rick

 

[jaa241]

Awesome man! I am glad you upgraded to the pertronix 2. Your boat will appreciate you so much more and will run healthier.

 

[jaa241]

Also,I bet if you try to fire your boat up after it warmed up without advancing the throttle it will start just like a car. ( May need to adjust the carb).

 

[Motodox]

Thanks everyone! And yes it fires right up just like a car. No throttle .. It's amazing!

 

[biggjimm]

Great! I knew you'd get it. It's a good feeling to finally. Get it going isn't it?

 

[SSTKO81]

I recently had a similar issue with mine which also has the flame thrower coil... A auto mechanic friend of mine suggested that those coils are designed to run off 12v, not the 4-7v provided through the resistor wire. I tried this and the engine fired off fine. Just a thought.