1987 Mercruiser 3.0l, no spark on Hot Engine

[Dravven]

I have a 1987 mercruiser 3.0l with an EST ignition installed. The last two times I have taken the boat out, it starts up initially and runs fine. After cruising for 10-20 min, I shut the engine down. The first time, I sat for 20 minutes with the engine off. When I went to restart, it would not start. I pulled the wire off the coil and had a very, very weak spark. I pulled the Dis cap off and the rotor was beat. Repalced both cap and rotor the next day. I started it up with muffs on, and I thought the problem was solved.
Fast forward to today. Took the boat out and the very same problem happened. I was by myself so I could not check for spark. But when I got home I pulled the plugs out and they were wet, indicating a no spark issus again.
I think maybe the ignition module may be bad, does anyone have any testing procedures for this? Any help would be appreciated.

 

[Dravven]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

Nobody has any help for me at all? Thank you in advance to anyone who can offer assitance.

 

[Spare_Time]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

Nobody has any help for me at all? Thank you in advance to anyone who can offer assitance.

Sounds like a coil issue to me. Have you replaced the coil recently? If the coil is overheating it will throw a weak spark when hot. If you are running the boat out of the water, is the engine cover off? This is probably enough to dissapate the heat and let the engine run fine. If the cover is on then the heat builds up and will cause problems. Also, check your coil to see if It needs an external resistor.

Engines need three things to run. Air, Spark and Fuel. Eliminate the problem areas and focus on what's left...

Hope this helps!

 

[Dravven]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

I am picking up a coil tonight. I guess I will see if that works. Is it safe to run the boat with muffs on for extended periods of time?

 

[Spare_Time]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

i don't see why you can't leave it running with the muffs on...just watch your engine temp! keep the cover closed and let 'er rip. I would keep RPM in the 1500 range...

 

[Dravven]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

Update...Picked up the coil tonight but did not install it. I don't like just throwing parts at things...Anyway, ran the boat with muffs in hope of reaching the same conditions as the no spark yesterday. Unfortunately, I can not get the boat to temp, running at 1500 rpms. So of course the boat stops and starts fine. I tested the coil and it tests out fine cold.

I did notice that the gray lead for the tach was in pretty poor shape. Someone had used a wire nut to splice the wire and it was filled with rust. I have heard that possibly a bad tach lead could cause a hot no spark condition. Can anyone confirm this? I understand that people have other lives than this forum, but thank you to anyone who can offer assitance.

The next plan is to pack my paddles and head for the lake tomorrow. Hopefully I can figure this out once I get the engine hot.

 

[supercab78]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

Clean up any and all conections on the primary ignition system from ign switch on back. You may be getting a voltage drop as resistence builds do to bad connection. There is good chance it's coil as stated above. I carry an extra in my boat. Maybe take a volt meter and test light out with you to diagnose it, that was the only way I fixed my problem once. I assume EST is electronic conversion, If so they have been none to fail. Good luck!

 

[chiefalen]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

Don s posted this hope he doesn't mind me posting this. Best list I ever saw.

http://forums.iboats.com/showthread.php?t=167035

 

[Dravven]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

Thanks for the list, it IS a great explanation of how to troubleshoot a starting system. Unfortunately, my problem lies in the ignition system. The engine always cranks over, hot, cold, whenever. My no start problem is due to no SPARK once the engine is to temperature.

Thanks anyway

 

[gmendozatp]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

hello having same problem.i change the condensor in distributor cap and wire does not heat up.still have not test on water.but it is a cheap try 5.00bucks at westmarine.will post my result as soon as i can

 

[Rat Capri]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

I have a 1987 mercruiser 3.0l with an EST ignition installed. The last two times I have taken the boat out, it starts up initially and runs fine. After cruising for 10-20 min, I shut the engine down. The first time, I sat for 20 minutes with the engine off. When I went to restart, it would not start. I pulled the wire off the coil and had a very, very weak spark. I pulled the Dis cap off and the rotor was beat. Repalced both cap and rotor the next day. I started it up with muffs on, and I thought the problem was solved.
Fast forward to today. Took the boat out and the very same problem happened. I was by myself so I could not check for spark. But when I got home I pulled the plugs out and they were wet, indicating a no spark issus again.
I think maybe the ignition module may be bad, does anyone have any testing procedures for this? Any help would be appreciated.

classic example of a faulty ignition module, runs fine when cold then misses, dies and/or will not restart when hot.....that's my .02

 

[chiefalen]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

You ever do a full tune up on this motor?

Good cables and connections at the battery?

Clean, and shiny ?

Good connections at the starter, clean and shiny ?
Disconnect the battery when you do the connections at the starter.

Follow the neg cable to the ground connection at the motor or bell housing, remove and clean shiny and re-install.

Now see if it still don't start hot? If it doesn't, pull the main plug, it clean in there? Green ?

Still don't start hot ?

Run a jumper wire from the battery to the coil, it start hot?

DO NOT LEAVE JUMPER WIRE ON, JUST TO TEST IT.

It got to start with a jumper wire, then it's the solenoid.

Get back to us after you do the above and let us know what happened.

 

[Don S]

Re: 1987 Mercruiser 3.0l, no spark on Hot Engine

This thread is from July 21st, 2008, 05:24 PM
I would hope he has already fixed this problem.