1997 7.4 bravo carb no spark

LunaSeaRay

New Member
Jun 3, 2013
11
Baltimore
Boat Info
1997 SeaRay Sundancer 270
Engines
7.4
Hi all. I’m desperate for help with my 1997 sea ray 270 Sundancer, single 7.4 in Baltimore. My father and I have spent 20+ hours over 5 months trying to get it to start.

There is power going to the coil, but nothing coming from the coil. We have replaced the coil. We have bypassed the neutral safety switch in the throttle. We have grounded out the coil. The batteries and battery charger are new. I replaced the distributor (not getting power anyway) and most other normal parts. We tested the ignition and traced the neutral safety switch wires as far as we could.

I last fired it up in June and once I pulled out of the slip, it shut off. You can crank it for hours and hear bubbling noises from the stern drive but it will not fire. There is definitely gas in the carb.

We have been through the mercuiser manual twice and checked all the water temp/oil pressure sensors by shorting them and watching the needle flip.

The one issue I found when the boat shut off in June is that an audible alarm sounded that would only since by turning off the red ignition switch on the throttle. I finally got that alarm to stop sounding when I located a wire that came off the automatic choke.

Does anyone have any suggestions? Our last hope is that one of those little control modules mounted behind the motor, around the risers may be bad. There doesn’t seem to be a way to test them and they may be hard to find replacements.

Any help is much appreciated. My father is a mechanic but has never dealt with boat issues like these.

Thanks in advance.
 
Is this a Thunderbolt 4 ignition? The sensor in the distributor was updated from original. Went thru this this summer.
Thunderbolt Diagnostics.jpg
 
Thanks for the reply. I have the thunderbolt V and we went through the diagrams twice checking each wire for 5v 12v etc per the manual. The ignition control module external to the distributor is the only component I haven’t replaced now. I replaced the ignition control module inside the distributor twice and noticed the first time that the rubber going through the distributor was worn greatly, maybe even burnt.

I’ll try to find that control module to replace as well. Like I said every wire has the proper voltage, resistance, whatever leading up to the coil.
 
The thunderbolt v ignition control module I have is part # 806959-4 which does not appear to be sold anywhere. Does anyone know if I can use the thunderbolt IV module, or recommend replacing the whole system?
 
It's too bad you didn't realize the ignition module was the problem before replacing all the other components. I was lucky with mine and it was only the $40 sensor. The module was $800. There are complete after market marine grade ignition systems available for much less than that. You may want to look in to them. Not sure for the 7.4, but I remember when I was looking into them, there were differences in the drive gear for the distributor on the 5.7's. May have just been a flat/roller cam thing. Good luck!
Edit; You may want to double check the wire color to your choke. I have an ignition wire hanging out of the harness next to mine. If it is grounded it will not fire.
 
Thanks. I will find a module eventually I’m sure. I have all winter. I was hoping someone had an idea that we hadn’t tried. Often people talk about throttle position sensors - but I think that’s on fuel injected models. I haven’t taken apart the stern drive lube oil reservoir and cleaned that sensor yet, but I hoped grounding the coil would have eliminated that.

When we grab those harnesses behind the motor, especially the circular one, every so often our moving those wires will cause the alarm to chirp. Still I think grounding the coil and bypassing the neutral safety switch should have bypassed that mess.

Thanks
 
Welcome to CSR!

It can be frustrating chasing a no-start condition. In your case, you have an advantage because it has a carb. The Thunderbolt Vs are not diagnostic friendly and expensive to repair. I lean toward replacing the system since you do not have an ECM controlling fuel injection. The cost of buying a ignition control module.....easily justifies replacing the system. If you could post the engine serial number that would be helpful in confirming a few things.
 
Thanks! I’ve been lurking these forums for the 6 years I’ve owned the boat.

Serial number 0K162953. Left hand bravo motor with drive serial number 0K181744 bravo III.

Repairs take long because I live in Central NJ. Boat is my Baltimore condo when I can’t work from home.
 
i went down the exact same path on a previous boat....

do yourself a favor and install a Delco marine ignition system and throw the Thunderbolt crap as far as you can into the ocean.....when i bought the Delco system it was around $400 and included everything needed.....very easy installation.....after that the engine never failed to start on the first rotation when the ignition switch was turned until the day i sold the boat a few years later....

good luck....
cliff
 
Last edited:
do yourself a favor and install a Delco marine ignition system and throw the Thunderbolt crap as far as you can into the ocean.....

This made me laugh out loud!
(And it’s good advice too)
 
This made me laugh out loud!
(And it’s good advice too)


i spent almost 2 years (off and on) trying to track down an intermittent loss of spark on a 1998 5.7 carb'd engine with the TBV ignition system.....after much help from many CSR members (especially 'PlayDate' - Master Mechanic) we finally determined the $800 ignition module was bad and they are like hen's teeth to find, even used...instead i paid half that price for the entire Delco ignition system and never looked back....

cliff
 
I'm with Cliff on this.

7.4 Bravo engine 0K162953

Thunderbolt V Ignition Control Module for your engine (and you keep your old distributor):
https://www.perfprotech.com/icm-conversion-kt-806959a01/product/138350

$547

Delco Voyager:
https://www.ebay.com/itm/New-7-4L-4...dExHomeDelivery!22124!US!-1:rk:2:pf:0&vxp=mtr

$345.95

You may be able to find it cheaper but this kit includes the plug wires and is plug and play.

John

Hey John,

I replaced my distributor a few years ago with a Mallory Marine Magnetic Pickup mechanical advance distributor. You’re saying that’s not compatible with Delco’s module and the distributor needs replaced again? It was a lot of work last time getting the variable timing set with the timing light. Is that the same case with the Delco set?

Thanks!
 
Hey John,

I replaced my distributor a few years ago with a Mallory Marine Magnetic Pickup mechanical advance distributor. You’re saying that’s not compatible with Delco’s module and the distributor needs replaced again? It was a lot of work last time getting the variable timing set with the timing light. Is that the same case with the Delco set?

Thanks!


I had to reread the entire post to remember this one......

Help me out..... do you still have a no start condition? Your original post said you had a Thunderbolt V distributor. In regards to the Mallory....I didn't say it wasn't compatible.

That said......I am suspicious that the coil is not being triggered. If you are using the Mallory.....it needs to be wired in a specific way with a load resistor in the circuit or it will eventually fry the amplifier in the distributor.
 
I had to reread the entire post to remember this one......

Help me out..... do you still have a no start condition? Your original post said you had a Thunderbolt V distributor. In regards to the Mallory....I didn't say it wasn't compatible.

That said......I am suspicious that the coil is not being triggered. If you are using the Mallory.....it needs to be wired in a specific way with a load resistor in the circuit or it will eventually fry the amplifier in the distributor.

Correct still no start. Thunderbolt V, but I replaced the distributor a couple years ago with a Mallory when the old pickup rusted out. Mallory plugged right in.

I don’t mind replacing the distributor again. I thought I just needed to replace the ignition module though. No luck finding a used one.

Thanks!
 
Hopefully my last question. I’m getting ready to install the Delco Voyager EST kit.

What do I do with the old thunderbolt V ignition module that we suspect is bad? The instructions only address the parts that came with the kit - distributor, coil, wires, leads. It doesn’t address the old module.

Should we remove the module? Picture of module shown.

Thanks!
 

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Hopefully my last question. I’m getting ready to install the Delco Voyager EST kit.

What do I do with the old thunderbolt V ignition module that we suspect is bad? The instructions only address the parts that came with the kit - distributor, coil, wires, leads. It doesn’t address the old module.

Should we remove the module? Picture of module shown.

Thanks!

you do not need the old Mercruiser ignition module with the Delco ignition system.

cliff
 
I know this is a very old thread, and I'm hoping someone will still get this. I have an identical problem. My motor is 1995 7.3, or 454 Bravo III. For two years I have fought a no start problem. The marina, I've taken it to has replaced coil two years in row, and last year included the ignition module inside the Distributor and mechanic says it runs, but it just cranks at home. I'm trying to run it down myself, and am looking at two modules attached to the back side of the distributor. According to manual, one is another ignition module or maybe, external ignition module, along with one called a "Knock control Module". As posted before the part 806959-4 (external ignition module) is kinda expensive and hard to find. Others here talked about changing to a Delco ignition system. Where would I find this system and what happens to the wires coming from the "Knock control Module"?

Thanks for any help
Gary
 
Check out DUI..Davis Unified Ignition. Lots of happy customers. Simple and reliable.
 
Gary,

I chased a similar problem two years ago on a customer's boat. The engine would crank and not fire. Every once and a while it would start but then it wouldn't. After swapping a number of ignition components.....we found that there was intermittent voltage at the + side of the coil (aka the purple wire).

We ran a jumper from the starter to the + side of the coil and the engine instantly fired up and restarted without issue. So, you may want to try that to see if the purple wire has been compromised somewhere along its path.

Let us know.
 

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