4.3 still no start

al0311

Petty Officer 3rd Class
Joined
Jul 29, 2017
Messages
97
Hi guys I still looking to solve my no start problem. Long story short I have a 1990 4.3 mercrusier, or so I think, that is not giving spark and Turning over. I think I have rulled out the ingnition coil as the culprit by bench testing it. I have also replaced the point and condensor in the distributor and set the gap with a feeler gague. But, the motor still will not start. At this point I’m kinda at a lose. I have tried to do every test I can in the Manuel and due to not being able to transport the boat to a mechanic I’m stuck looking at it in the driveway. I really don’t want to start spending money on parts that might not solve the problem. Any other help is appperciated. Thanks
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
51,252
it is never the coil.

go back to the points. file them (you even have to file new points), gap them, use a dwell meter and set dwell, then install cap and rotor, fire it up and set timing.

it is the opening of the points that collapses the magnetic field in the coil which generates the spark.
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,449
Try to get a Dwell meter to set the points. A feeler gauge setting is always wrong, when you use a dwell meter it puts the points at the correct setting. Clean the points before setting the dwell. DO NOT try to reset them with a feeler gauge.
With the points open and the ignition on you should have current to the points. If not, disconnect the wires on the negative or distributor side of the coil and only re attach the wire from the distributor to that post. You may have a shift switch problem grounding the ignition.
 

al0311

Petty Officer 3rd Class
Joined
Jul 29, 2017
Messages
97
Okay just want to say thanks guys for the feed back. So far what I did was file the points reset the gap like said, and hooked up my multimeter with a dwell setting. Cranked the motor over and I wasn’t getting any reading at all on the dwell meter ??? I’m lost haha
Kenny Nunez in response to your comment. Question for you . Is there a way to test for power to the points ?
 

al0311

Petty Officer 3rd Class
Joined
Jul 29, 2017
Messages
97
Holy carp !! So I disconnected the yellow green wire from the negative coil and it started to turn over. Needless to say it wouldn’t stay turn fully on but was turning over . I’m not quite sure what to do with this new found info but I was so excited to see it turn over I almost jumped outta the boat
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
51,252
You really need to read up on breaker point ignition. Just google it. Plenty of step by step how toos
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,449
One of the best tools to have in your boat tool box is a TEST LIGHT. Make sure it is a good one from Sears or one of the tool manufacturers. The cheap ones usually do not last. A volt meter is also a great help, together you can diagnose any electrical problem.
With the ignition on and the points open you must have at least 12 volts reading on both sides of the coil, with the points closed the should be around 8 volts. If the voltage does not drop when the points are closed then the points are either not making contact due to not being clean or the carbon material has absorbed moisture. If they have what appears to be small white dots on the mating surfaces all the cleaning, scraping etc. is a waste of time. While the engine may start it will not run right or for long. Be sure to only use genuine Mercruiser replacement ignition parts.
 
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