Will not crank, no fire

Has the starter or the ignition switch been messed with? Sounds like the wires are messed up, like, not hooked up to the Run terminal.

Will not crank, no fire

I have a 5.7omc with a thunderbolt ignition. When you try to start ..no fire, then when you switch it to off go get a breif fire. could the ignition mod be bad. The coil is ok.I checked the price on a new module and ohhhhhh brotherrrrrrrr. It looks as if the boat has been changed from a points system to a electronic.

Re: Will not crank, no fire

The motor came complete from another boat that had 25hrs on it. The motor would crank when it was first installed. We changed the starter. All was fine. then today. dead. It is wired like a points system with two wires from the starter, one to the coil from one side of the starter and one from the other side to..... I think the key side . Thanks

Re: Will not crank, no fire

An OMC with a Thunderbolt ignition?

Re: Will not crank, no fire

Sounds like you have more than one issue. With electronic ign there is no wire from the solenoid to the the coil. That would only give 12v during cranking. If it had points before, the wiring loom will be different and you will leave that wire disconnected. The conversion kit includes wiring instructions for the coil/module etc. The solenoid terminal runs thru a neutral safety switch, a slave solenoid and then the starter. Your going to need a test light and work your way through starting circuit. Don S. has a diagram, I beleive in the faq's. Once you have the starter working properly you can start again with the light or meter and recheck how the ign is wired. A manual and wiring diagrams will be necessary.

Re: Will not crank, no fire

Thanks. The starter is wired with two small wires on the sloenoid. One to the coil and one to the slave solenoid.I thought it was odd for way it was wired but it ran fine. Should ther only be one small pin on the starter solenoid with both wires connected.

Re: Will not crank, no fire

The wiring harness came on the motor and was running. What did you mean by Don S ? Thanks

Re: Will not crank, no fire

Thanks. Installed a new battery/cables/ends. Checked all wiring. All clean and ok. The motor was cranking fine all week then it will spin and fire once and awhile then tries to crank when you let off of the key switch. I do have one purple wire from one side of the starter and one yellow/red from/ to the helper solenoid from the other side of the starter.

Re: Will not crank, no fire

The wire from the 'r' terminal on the starter is not necessary with elctronic ign. The coil gets a full 12v with the ignition key in the run position. You'll have to check the voltage down the line from the key to the starter and see where you lose it. Connections need to be clean and tight. (looks clean is not good enough). Remember the starting circuit and ign circuit are seperate other than the wire from the starter solenoid to the coil, which you won't use if you have electronic. Battery cables need to be clean and tight and in good condition as well. Clean the battery ground at the engine too....

Re: Will not crank, no fire

You have a classic example of a bypass resistor failure.

The bypass resistor only allows about 9 volts to the coil, On the run circuit, so that you don't burn it (coil/points/EDI unit) up with alternator voltage.

Us old guys, know that.

1. If the coil has 12 volts+ (KEY ON ENGINE OFF-ENGINE CRANK-ONLY, That is OK. The voltage should drop to about 9V with the KEY-ON, ENGINE OFF.

2. There should be a resistor, in line, to drop the voltage to no more than 10 volts.

3. If not, intsall one, on the RUN circuit.

4. Note: your coil may already be toast. Replace.

Re: Will not crank, no fire

Straight from the pertronix installation instructions: How to correct a LOW voltage problem -
First, if you have an external resistor, connect the red ignitor wire to the ignition wire
PRIOR to the ballast resistor. If you do not have a ballast resistor you must locate a
12-volt source that is controlled by the ignition switch.

I use MSD on my boat, and it is virtually the same instructions. As I stated before. You will
have to isolate the starter issue and resolve it. Once it is cranking consistantly, you can
troubleshoot your ignition issue. Coils are made with and without resistors and which one you need
depends on what ignition system has been installed. You have stated it was Thuderbolt, but that is a
Merc product. You say you are running an OMC. Clarify what it is you have for specific instructions.

Re: Will not crank, no fire

I have a 1989 four winns with a 5.7 omc 310 hp. The motor was installed several weeks ago from a wrecked boat that had 25hrs on it. It has a mercruiser electronic ignition installed, go figure..... The motor cranked fine for several days. Then the starter would turn but seemed to fire only once and awhile until you let go of the key then it will try to crank. The wire harness was with the motor. The motor that was in the boat was a 5.0 ford with a points system. ignition.Thanks

Re: Will not crank, no fire

Look just above the starter on the bellhousing flange, there is a metal tag with the Mercruiser Serial Number.
What is that number.
It doesn't matter what it came out of or how many hours it has on it, what matters is finding out what ignition system you have.

Re: Will not crank, no fire

Being you have a merc ignition, you will have to figure out which manual would best suit the motor/ign package. I guess there is a verbage issue for me here. When you say won't crank, I was getting the starter would not turn the motor. Seems it turns over fine but will not fire/run. If it ran and no longer does, first thing is the tuneup. 25 hrs doesn't mean much. Check compression, if you haven't already. Replace the coil with the proper one for your ign system. It's cheap. Cap/rotor/plugs/wires. Fuel filters, water seperator etc. While your in the distributor, look at the pickup coil. Merc used a metal base (oem) and they rusted and stopped working. There is a replacement I got from the merc dealer here, (yes i had this issue), that has a bakalite body, costs half as much and has no metal to deteriorate. I don't have my manuals here, but there is a testing procedure for the pickup coil. The modules are another issue. I am not aware of any testing that can be done. At least the merc dealer here states that. He also told me that it either works or doesn't. I found that to be untrue. Mine ran, but ran like crap. After a complete ign service, paid the 400 bucks for the new module and all was well. Trouble is everything in the ignition has to be ruled out or your taking a 400 dollar gamble. Once you rule out the ignition, the carb/fuel would be next.