Engine just stopped

[Farmboy666]

Started the engine and sat at idle for 5 minutes. Started off down the lake and running fine. Then engine just shut off like somebody flipped a switch. Got the boat home and started troubleshooting. Turns over fine. Won’t start with starting fluid in carb so not fuel related. I have power to both positive and negative sides of coil which I know on a points distributor means open circuit. With a test light bright light on either side of coil but dim light in middle where coil wire attaches. With a spark tester no power from coil to distributor. New coil same result. I’m thinking Thunderbolt iv electronic ignition module has died. Does anybody see something I’m missing or have any troubleshooting advice on which way to go

 

[Bill Curtis]

If you have a dwell meter, connect it up and it will show a dwell, while cranking engine, if the ignition module in solid state ignition and coil are working correctly. If no dwell, the coil, module inside distributor or ignition module (or a crappy wire connection) are bad.

I included the Thunderbolt manual for 4 and 5.

 

[Farmboy666]

Thanks, that will be very helpful. Will test today.

 

[Farmboy666]

Used the test method and it shows bad ignition module. Bought
one off eBay and seller wasn’t sure if it was good or not, so I took a chance and it also tested bad. Still not 100% sure that’s what the problem is but can’t find anything else wrong. Have a Delco ignition kit coming in a few days and scraping the Thunderbolt. It’s a fairly straightforward install, hardest part will be getting TDC on the compression stroke because the engine is such a tight fit and I don’t want to start taking water jackets off to get to the number 1 plug so we’ll see. If anybody has any suggestions they are welcome.

 

[Thornton69]

First off, make sure the shift interrupt switch is not causing your ignition problems.
As far as replacing the distributor. #1 TDC is really not that important. Pay close attention to which cylinder (ignition wire) post on the distributor cap the rotor is pointing to before removing the old distributor. Drop the new distributor in with the same alignment. Keep in mind it may change slightly if the crankshaft has to be turned to engage the oil pump drive to fully seat it. Adjust distributor slightly to compensate any movement. Warm up engine and follow the timing instructions that came with the Delco kit. Do not load the engine if you have skipped base timing it.
The last couple EST kits I installed, used full advance of 28 at 4000 rpm for final adjustment I believe, but they were the later Vortec engines.

 

[Bill Curtis]

Have you changed the pickup module inside the dist? Don't know if there is any way to test the module. I would do that 1st, before pulling distributor and scrapping the Thunderbolt. Always found Thunderbolt a very good setup for what it is..

If you are doing the change, pop off the dist cap, rotate crank until rotor points to # 1 plug wire position and then align crank to TDC on timing mark. Pull out dis. After pulling out dist DO NOT TOUCH THE STARTER.

Finding #1 TDC isn't earth shattering. Pull out #1 and have someone hit starter with your thumb over the plug hole. Compression will blow your thumb out of the hole coming to tdc.

 

[Skybolt]

... Finding #1 TDC isn't earth shattering. Pull out #1 and have someone hit starter with your thumb over the plug hold. Compression will blow your thumb out of the hole coming to tdc.

Then line up the timing mark on the front of the engine to 0 degrees and your at top dead center.

 

[Farmboy666]

First off, make sure the shift interrupt switch is not causing your ignition problems.
As far as replacing the distributor. #1 TDC is really not that important. Pay close attention to which cylinder (ignition wire) post on the distributor cap the rotor is pointing to before removing the old distributor. Drop the new distributor in with the same alignment. Keep in mind it may change slightly if the crankshaft has to be turned to engage the oil pump drive to fully seat it. Adjust distributor slightly to compensate any movement. Warm up engine and follow the timing instructions that came with the Delco kit. Do not load the engine if you have skipped base timing it.
The last couple EST kits I installed, used full advance of 28 at 4000 rpm for final adjustment I believe, but they were the later Vortec engines.

I checked shift interrupt switch today and seems fine. I think the test procedure that Bill Curtis attached takes care of it. My concern with the timing was not so much the number 1 cylinder but more the compression stroke because the plugs are so hard to get to. I think I’ll take the valve cover off and do it that way. Thanks for the info.

 

[Farmboy666]

Have you changed the pickup module inside the dist? Don't know if there is any way to test the module. I would do that 1st, before pulling distributor and scrapping the Thunderbolt. Always found Thunderbolt a very good setup for what it is..

If you are doing the change, pop off the dist cap, rotate crank until rotor points to # 1 plug wire position and then align crank to TDC on timing mark. Pull out dis. After pulling out dist DO NOT TOUCH THE STARTER.

Finding #1 TDC isn't earth shattering. Pull out #1 and have someone hit starter with your thumb over the plug hole. Compression will blow your thumb out of the hole coming to tdc.

The test procedure you attached covered the pickup module and it tested ok. Plugs are hard to access so taking the valve cover off to see valves. Thanks for the attachments. They really helped.

 

[scoflaw]

I checked shift interrupt switch today and seems fine. I think the test procedure that Bill Curtis attached takes care of it. My concern with the timing was not so much the number 1 cylinder but more the compression stroke because the plugs are so hard to get to. I think I’ll take the valve cover off and do it that way. Thanks for the info.

That's crazy, how do you do a tune up?

 

[Farmboy666]

I haven’t had to change the plugs on this one yet. I owned the same boat in the 90s and took it to a marine mechanic for the plug change and when I picked it up he said he would never do it again. It’s doable just not fun.

 

[Farmboy666]

Installed Delco ignition kit. Boat starts faster than it has been and runs great. Install was not difficult. I removed the valve cover to verify TDC on compression stroke. Some wiring has to be done. Shift interrupt switch needs to be changed from grounded to positive when engaged. My guess is with the hard starts and stalling at idle when cold which I thought was carb related was probably the Thunderbolt IV on it's way out.