4.3 will not start, No spark

[Mark in NC]

Started to winterize the boat. It is 2003. The motor is 4.3 with a tag on the block that says Serial Number M377272 Mercury Marine Brunswick Corp. Fon Du Lac WI.
It started and ran for a short time then abruptly quit. I suspected electrical problems since it just quit like turning key off.
First attempt to repair was replacing the coil. No change. I replaced the coil lead from coil to distributor as well since old was was stuck in coil and was damaged from trying to remove it. I looked at distributor cap and found a lot of carbon build up on each of the rotor buttons.
I removed a spark plug and found it to be very black but not oil covered, like it was running very rich. I tried to see a spark but never was able to see this by grounding plug on block.
Does anyone have suggestions for replacing the distributor cap, high tension leads and spark plugs? Is there any difference for a marine component as compared with standard ignition components?
This motor was dieseling when the key was turned off during the summer which I felt indicated a rich running condition but it never had trouble starting. Thanks for any suggestions.

 

[Roger baril]

Change the key switch it could be your answer

 

[Espos4]

No spark at the plugs so start working backwards.

Do you have spark from the coil?

 

[Mark in NC]

Change the key switch it could be your answer

I have voltage at the coil so I believe key switch is working

 

[Jimmy Buoy]

I suspect that your serial number is not M377272 but 0M377272 which is a 4.3L MPI with either Alpha or Bravo Drive (most likely an Alpha for a 18' boat).

MERCRUISER : 4.3L MPI ALPHA/BRAVO : 0M300000 THRU 0M614999 | PerfProTech.com

Online shopping for MERCRUISER : 4.3L MPI ALPHA/BRAVO : 0M300000 THRU 0M614999 Parts & Accessories

www.perfprotech.com

When you turn the key to ignition do you still hear the one long beep (indicating all is good with the system)?

When you turn the key to "ignition" do you still hear the fuel pump pressurizing?

It seems unlikely that all of a sudden the engine goes from running to no spark on any cylinders without involving a simpler issue. It may be as simple as a blown fuse. There is a fuse block on the back end of the engine that contains 3-4 little blade fuses. It has a black cover and is something easy to check by removing the cover and exposing the fuses.

Also, do you have a lanyard cutoff switch that may have been triggered "off"?

 

[Mark in NC]

No spark at the plugs so start working backwards.

Do you have spark from the coil?

 

[Mark in NC]

I will need to verify spark from coil. I guess a simple method of screwdriver from distributor end of cable to a ground would tell me that. I am away from boat currently so will plan next steps to have what I need to make progress

 

[Mark in NC]

I suspect that your serial number is not M377272 but 0M377272 which is a 4.3L MPI with either Alpha or Bravo Drive (most likely an Alpha for a 18' boat).

MERCRUISER : 4.3L MPI ALPHA/BRAVO : 0M300000 THRU 0M614999 | PerfProTech.com

Online shopping for MERCRUISER : 4.3L MPI ALPHA/BRAVO : 0M300000 THRU 0M614999 Parts & Accessories

www.perfprotech.com

When you turn the key to ignition do you still hear the one long beep (indicating all is good with the system)?

When you turn the key to "ignition" do you still hear the fuel pump pressurizing?

It seems unlikely that all of a sudden the engine goes from running to no spark on any cylinders without involving a simpler issue. It may be as simple as a blown fuse. There is a fuse block on the back end of the engine that contains 3-4 little blade fuses. It has a black cover and is something easy to check by removing the cover and exposing the fuses.

Also, do you have a lanyard cutoff switch that may have been triggered "off"?

Yes long beep is there and fuel pump pressurizes. Checked lanyard kill switch

 

[boatrboy]

One year leaving a dock with my buddy, he started the boat to warm it up earlier. Then when we started to leave, the boat just stalled as you described. No spark. 4.3 carbureted engine. Turned out to be the module in the distributor. Iirc it was about a $100 part.

 

[Mark in NC]

One year leaving a dock with my buddy, he started the boat to warm it up earlier. Then when we started to leave, the boat just stalled as you described. No spark. 4.3 carbureted engine. Turned out to be the module in the distributor. Iirc it was about a $100 part.

Yes, I will pursue that option. I am suspecting not getting the spark from coil is my thought and new coil didn’t fix that problem. If I go from there on out I will know status of everything. I have no background with this boat and any maintenance history. Just as dirty spark plugs make me want to check all of them! Curious it looks excessively rich

 

[Jimmy Buoy]

No distributor module in that 4.3 MPI engine.

It gets it's timing info from the crank angle sensor on the timing chain cover just under the crank pully.

If the crank sensor fails it will NOT show via any smartcraft warning beeps nor will it show as a code on a Rinda reader.

 

[Mark in NC]

No distributor module in that 4.3 MPI engine.

It gets it's timing info from the crank angle sensor on the timing chain cover just under the crank pully.

If the crank sensor fails it will NOT show via any smartcraft warning beeps nor will it show as a code on a Rinda reader.

Great information to know. I am trying to learn about this boat as I have never had to do any of the maintenance. It has been stored inside with about 400 hours on meter. My dad bought it and he has gotten very sick. I have taken responsibility for it and am not able to hire out maintenance and usually do all my own equipment repair and maintenance. I own four Hobie 16 from early 80’s so not much experience with power boats. They are tough to get to things. I have gotten good at hanging upside down and removed the interior panels to help with repairs.

 

[Mark in NC]

Merry Christmas, BTW

 

[boatrboy]

No distributor module in that 4.3 MPI engine.

It gets it's timing info from the crank angle sensor on the timing chain cover just under the crank pully.

If the crank sensor fails it will NOT show via any smartcraft warning beeps nor will it show as a code on a Rinda reader.

I did not know it was a mpi at first. The I looked up his serial number and saw this which has me curious. Isn’t number 6 a replaceable module?

 

[Fun Times]

Happy Holidays to all.

For better clarification purposes of offering help regaining spark, the engine in question serial number 0M377272 shows the engine to be carbureted.

0M377272 = MERCRUISER 4.3L ALPHA 2 PC Exhaust, Model Number 4211025PS.

MERCRUISER : 4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 : 0L010044 THRU 0M614999 | PerfProTech.com

Online shopping for MERCRUISER : 4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 : 0L010044 THRU 0M614999 Parts & Accessories

www.perfprotech.com

You may want to search MerCruiser thunderbolt 5 troubleshooting as there are multiple places that offer a troubleshooting test guide to follow.

There is a sensor under the distributor cap for this engine also item number 6 but is a different design than the EFI design asked about above. The one above in post number 14 would be considered a Cam Shaft sensor and it wasn't utilized until about the end of 2005/start of 2006 model years.

Hope this helps, good luck.

 

[Mark in NC]

Yes, Carburetor on this one. I’ll

Happy Holidays to all.

For better clarification purposes of offering help regaining spark, the engine in question serial number 0M377272 shows the engine to be carbureted.

0M377272 = MERCRUISER 4.3L ALPHA 2 PC Exhaust, Model Number 4211025PS.

MERCRUISER : 4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 : 0L010044 THRU 0M614999 | PerfProTech.com

Online shopping for MERCRUISER : 4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 : 0L010044 THRU 0M614999 Parts & Accessories

www.perfprotech.com

You may want to search MerCruiser thunderbolt 5 troubleshooting as there are multiple places that offer a troubleshooting test guide to follow.

There is a sensor under the distributor cap for this engine also item number 6 but is a different design than the EFI design asked about above. The one above in post number 14 would be considered a Cam Shaft sensor and it wasn't utilized until about the end of 2005/start of 2006 model years.

Hope this helps, good luck.

 

[Mark in NC]

Yes, two barrel carb. I’ll follow the suggestions there for better insight. Right now I am watching two year olds and it is impossible to concentrate ha ha

 

[Mark in NC]

Happy Holidays to all.

For better clarification purposes of offering help regaining spark, the engine in question serial number 0M377272 shows the engine to be carbureted.

0M377272 = MERCRUISER 4.3L ALPHA 2 PC Exhaust, Model Number 4211025PS.

MERCRUISER : 4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 : 0L010044 THRU 0M614999 | PerfProTech.com

Online shopping for MERCRUISER : 4.3L (GEN +) (2 BBL.) GM 262 V-6 1998 : 0L010044 THRU 0M614999 Parts & Accessories

www.perfprotech.com

You may want to search MerCruiser thunderbolt 5 troubleshooting as there are multiple places that offer a troubleshooting test guide to follow.

There is a sensor under the distributor cap for this engine also item number 6 but is a different design than the EFI design asked about above. The one above in post number 14 would be considered a Cam Shaft sensor and it wasn't utilized until about the end of 2005/start of 2006 model years.

Hope this helps, good luck.

This link

looks much more like what I have. I replaced the coil and lead from coil to distributor. Lead was damaged when removing it from old coil due to the male end being stuck in socket and came off of end of cable. Having only removed one spark plug and finding it black with soot makes me feel all plugs could use inspection. It rained here for 3 days so no opportunity to do anything.
I have been getting parts from local NAPA but find it frustrating because they often don’t have the correct part and aren’t able to look up part without an automobile make and model. The lead from coil to distributor for example was incorrect every time they tried to get one. I ended up getting one from a marine mechanic that was local to where boat was.

 

[dwna1a]

IF you have a Carquest near you, they sometime have marine parts.

Most of mine come from JEGs and Hardin Marine online.
By your photos she needs a complete tuneup. Trash the Thunderbolt stuff and get a Marine DUI distributor, just a suggestion