New to boats and about to burn down my boat. Need some help with wiring.

[jon1440]

I have a 4.3 mercruiser Mark V with the Denso control module. I'm not getting spark. Coil purple wire gets juice. I unhooked grey tach wire on negative side of coil just to eliminate a possible issue for trouble shooting. Still nothing. I bypassed fuel pump solenoid so pump comes on when key is in the on position, so pump is working. Crazy thing is, boat ran in the driveway one day and then the next, it doesnt. Kinda like at the lake, one good day and then the next Im dragging it with a 200' rope back along the shore to the dock. New coil also, which I made a jumper wire straight from the battery to the positive side of the coil to make sure it had 12volts. Still no spark out. I'm completely lost. Im also looking for a wirinig diagram if anyone can point me to the sticky if one exists. Currently there is only 2 wires that I can see that needs to be hooked up to the coil. Purple power and grey tach wire on the negative side. Also looking for the power and ground wire for the module. I have no idea which ones these are. I ran through the trouble shoot list and havent been able to perform the spark gap test but surely a new coil would provide a spark. Thanks in advance. Like i said Im new to the boating world, so bare with me. Thanks in advance

 

[nola mike]

I have a 4.3 mercruiser Mark V with the Denso control module.

No such animal to my knowledge. TB V maybe? Post a serial number, or at least engine year and we can help you better...

 

[Rick Stephens]

So everyone knows where to start, you should post your serial number and year.

 

[ROY WILLIAMS]

did you use a voltmeter .. voltage on the coil ...spark module are breaking down ..

 

[jon1440]

So everyone knows where to start, you should post your serial number and year

So everyone knows where to start, you should post your serial number and year.

You'll have to excuse my ignorance. Where can I find the serial number? Boat is a 2002 smoker craft. 4.3 mercruiser, carb, Has the denso module. On the denso box, numbers are 131800-7071

 

[jon1440]

did you use a voltmeter .. voltage on the coil ...spark module are breaking down ..

Just checked the coil again. upon cranking, Im getting 11 or so volts. Under 12 for sure. Yesterday I did put a jumper wire from battery to coil to make sure Im getting 12 plus volts and still nothing.

 

[jon1440]

can the coil plug wire be checked with an ignition strobe light gun? Ive tried this and gun is not flashing.

 

[jon1440]

Also the motor appears to have a crank trigger in the timing cover. To my knowledge this has never been hooked up and appears there is no other wires to plug in. I've had the boat 2 months and ran fine twice, and then instantly started in with the issue.

 

[ROY WILLIAMS]

can the coil plug wire be checked with an ignition strobe light gun? Ive tried this and gun is not flashing.

the module connector pins inspect it ..
the spark plug put on the wire out of the engine and see if the spark is a bright color .. or the spark is a dull color or no spark ..put the spark plug on a clamp to the engine block ...

 

[jon1440]

the module connector pins inspect it ..
the spark plug put on the wire out of the engine and see if the spark is a bright color .. or the spark is a dull color or no spark ..put the spark plug on a clamp to the engine block ...

Ill give it a go. I just went to look for the serial number and the air breather is supposed to have these but the owners prior must of replaced the cover and did not transfer the numbers over. So I don't have much to go off of for serial numbers, unless somewhere else.

 

[Rick Stephens]

Where to find Mercruier Stern Drive and Engine serial numbers.

Stern Drive serial numbers. (Continue down to the next posts for engine locations) ---------------------------------------------------------------------------------------------- All Mercury Marine serial numbers follow a particular format, be they Engine, Drive or Gimbal housing. Up to about...

forums.iboats.com

 

[nola mike]

Again, afaik no denso ignition systems in the 4.3... Someone correct me if I'm wrong.

can the coil plug wire be checked with an ignition strobe light gun? Ive tried this and gun is not flashing.

Yes, it can

Also the motor appears to have a crank trigger in the timing cover.

Don't know if they were installed on the Merc spec'd carb motors, but yours wouldn't use it. Is this the original engine? Maybe post some pics of your ignition setup.
Edit: rereading this, maybe I'm misinterpreting. There's a reluctor wheel under the damper pulley used for a CPS, but doesn't sound like that's what you're talking about

 

[Scott06]

The thunderbolt modules are made by denso. Here is the TB troubleshooting guide https://forums.iboats.com/threads/how-mercruiser-thunderbolt-ignition-systems-work.676476/

did u test the sensor inside distributor by tapping the wire to ground as seen in the guide?

some of the newer engine have crank sensor in timing cover. On my carbed 5.0 it is unused. If yours is wired up you have an efi or mpi engine that likely has different ignition

 

[AMMO DAWG]

I had an intermittent ignition on my 4.3, it had the Thunderbolt ignition, regardless I understand the frustration. Some on this forum might not agree, but I went to a Delco ignition system for marine use and man what a difference. Went from cranking to instantly firing up, not to mention a must simpler system. My original intention was to keep it stock, however if you can find a Thunderbolt Ignition Module open the old wallet wide! I followed the route outlined in the link below incorporating a relay and inline fuse for added protection. I added a waterproof box for the relay to keep it out of the weather. Just a thought, guess I should have asked up front is it a carbureted engine or EFI, if EFI probably wont be a good solution. Hang in there, been wrestling my own gremlins for some time now, keep at it and you'll get on the water soon!

 

[Scott Danforth]

Follow the troubleshooting guide that @Scott06 posted

If your trigger sensor in the distributor has only 2 wires, it may have gone south. The new design of ignition triggers have 3 wires

 

[Scott06]

Wiring diagram attached

 

[ROY WILLIAMS]

Ill give it a go. I just went to look for the serial number and the air breather is supposed to have these but the owners prior must of replaced the cover and did not transfer the numbers over. So I don't have much to go off of for serial numbers, unless somewhere else.

use the ohm meter to the gear shift switch ..take the wire off and test the ohms .. short/open .

 

[jon1440]

Curious if anyone would know if this solenoid runs the trim motor? Im going to replace the circuit breaker along with rotor, cap, plug wires, coil and plugs. The circuit breaker is basically none functional. These are seasonal items to check, possibly change regularly anyways. Its unfortunate I can't give a serial number for much more knowledgeable people here but Im tired of thinking how I just bought this thing and only had 1 decent day at the lake. My actual first issue with this thing wasn't even electrical, it was the syphon tube falling off into the tank. Previous owner made sure to top off the tank upon test cruise. 2 hours later I'm floating in the middle of the lake.

 

[jon1440]

 

[Rick Stephens]

Apparently 4.3L Vortec with Mercarb and ThunderboltV ignition. Makes it a '96 or later. Couple hundred horsepower.

That solenoid actually for the starter. The circuit breaker is for the entire system except the trim hydraulic motor.