Gasser Issues

[PaulJ]

I'm looking for opinions and insight...
B28 with 5.7L 350 Gas, FWC, Thunderbolt Ignition, 4BBL Carbs, Velvet Drives.

Had an enjoyable weekend running to and fro. Ran the boat for about 2.5 hours total on Sunday without problems... until about 3 miles out from the dock in the ICW. Port engine lost RPMs quickly and then rev'ed and then shut off.

I was able to restart and ran in neutral for a minute, it hesitated and shut off. Repeated the restart and ran in neutral for a minute or two. Seemed to be ok so I got her back up on a plane and ran the 3 miles to the dock without issue. Wanting to figure out what happened, I turned her around and headed back out into the ICW. Ran at various RPMs under load. No issues at any RPMs so I ran her out 3 miles and back.

Backing into the slip at idle, the engine shut down again. Restarted easily as before. Left her running in idle while I unloaded and washed her down. She shut off 2 more times as before while in idle.

It's fuel or fire (electrical)... right? I suspect in this order 1) loose connection; 2) Coil going bad; 3) Distributor pick-up sensor; 4) TB Ignition module.

Anybody got any ideas?

Thanks,
Paul J
1973 B28 - PALADIN

[Kevin]

Paul,
I am leaning towards fuel/carb since you said it lost RPM's then revved a bit before it stalled. Only one engine having problem right? If so that should eliminate the likely hood of clogged tank vent. I would suspect carburetor. Checking grounds are pretty easy so it can't hurt. If you don't find anything obvious you could swap carbs and see if the problem follows the carb.

[ljmauricio]

The symptoms are the same that I had a few months back. Run for a while, then shut down. Sometimes at idle, sometimes at cruise RPM. Run for a long time and shut down, or shut down after a few minutes. Replaced coil and external resistor. Didn't help. Checked for air leaks in fuel system. No help. After eliminating the fuel pump, a mechanic suggested a faulty ignition switch. Mine is simply on/off key with a separate start button. Swapped switches and problem fixed. If you have an ignition setup like mine, you can run a jumper from the positive coil terminal to a positive battery lug and that bypasses the switch. Hit the starter button, and engine starts. I posted this a few months back if you want to see what the group suggested.

[Yannis]

Like Kevin, I also tend to think it's carb related. Maybe a stubborn revolving piece of dirt that clogs and unclogs.

[TailhookTom]

What's the deal with your fuel tank? Could you have an ethanol issue?

Tom

[MarkD]

I have the same configuration. Mine is a 1988 model. A few years ago, I had an issue where the engine would run just fine and then just quit. It would often start right back up. Mine were ignition related. There is a sensor under the distributor cap that goes bad. It's a $50 part if I remember correctly. I replaced that which solved the problem. However, two years later, I had a similar issue on the other engine, which turned out to be the thunderbolt ignition module. After replacing one of each on separate motors, I never had an issue. PM me if you think it may be the Thunderbolt module.

[PeterPalmieri]

Fuel pump?

[PaulJ]

Thanks everyone for your inputs.

And thanks to Capt. Patrick for fixing my account as I've been locked out for a day!

Sounds like I have a few things to test to isolate the problem. My local mechanic said it could be a short in the Tachometer. Says it happens all the time. Grounding of + in the tach or wire and it shorts out the coil + and you shut down.

I installed a remote ignition/start switch and mechanical oil and temp sensors under the hood so i could run the engines while standing in the engine bilge. I only have the bridge controls and climing out of the bilge and up there without the ladder can be a pain when your trying to do things... Highly recommend doing this if you only have one station. So, I can isolate the engine from the harness and test the engine, isolated from the rest of the boat, i.e., tachometer. I have been wanting new guages as my SW's are original and have seen better days but hoping to defray spending money on that so I can buy more fuel. If its not the tach, I'll work through swapping one at a time the coil, sensor and TB module and see if the problem travels.

I can easily clean out my racors to see if there's any junk in them. Theres a small filter just inside the carb where the fuel line enters... I can check that too. I can service the air vent pretty easily. If its in the tank at the pick up... That would be a tough one. Ethanol has never gotten near my boat... At least I've asked at every fill up and here in FL we don't have the same ethanol regs as up north and most all marinas know the deal.

Thanks for the advice. I'll report any findings next week.

Paul J
1973 B28 - PALADIN

[STraenkle]

You have gotten some great advice here, one way I have used to find out whether gas or spark, when the engine shuts down, don't touch the throttle, take the spark arrest off and then pump the throttle, if you see gas squirt into the carb from the accel pump, you know it did not run out of fuel, the bowls are still full. If both engines did it, I would say water in the fuel. But only one does it. My guess, if the engine sounds fine and runs strong, then just stops, your loosing spark. Gas starvation usually has the engine sputtering and even backfire from the lean condition, then stops and usually wont start back up until you pump more fuel into the carb, assuming you have mechanical fuel pump.

I am sure you will find it. It sucks wondering if the engine is going to take a nap at the wrong time.

[Carl]

Water in fuel can show up on one side if pickups are at different heights.

Depending on your carb you can also get water and junk into bowls from a drip on top of motor. My Carters always had to be rebuilt for that reason...or at least taken apart and the bowls cleaned. But usually it just lost rpm and ran like crap. That final surge has me thinking fuel.


When she shuts off...do you smell fuel in carb? Does it squirt when you pump after it does like like STraenkle mentioned?


Intermittent problems...hate them.

[Capt Dick Dean]

Same problem... the little filter at the carb bad.

[PaulJ]

STraenkle - Neat trick. Didn't know that about the pump check. I'll definitely check that out.

It may sound funny, but it would be much easier if it just wouldn't start and run so well. If it didn't start and there was no spark... easy peezy. If it sparked, but no fuel... easy peezy. Something will finally show up. Just hoping I can get it to show up while testing it and that it just doesn't dissapear and then pop up it's ugly head right when I need the engine to be running.

[ljmauricio]

Seems like you've gone through everything I did with the same problem. Just couldn't believe it could be the ignition switch until it became the last resort. Switched it out with the other side, and now the other engine had the problem. New switch did the trick.

[PaulJ]

Well, that was easy! Planned my day around swapping parts between engines to figure out the problem. First things first, started both engines and got them to temp. Then I reached down and did the ole wiggle the wires test on the wires going from the distributor sensor to the TB module... And, engine shut off and the ground wire came off in my hand. Reconnected the ground wire and secured it reeeaaal good. That took all of about 2 minutes. Spent the rest of the day burning fuel and enjoying the water!

Thanks for all the ideas.

Paul J
1973 B28 - PALADIN

[Carl]

Well, that was easy! Planned my day around swapping parts between engines to figure out the problem. First things first, started both engines and got them to temp. Then I reached down and did the ole wiggle the wires test on the wires going from the distributor sensor to the TB module... And, engine shut off and the ground wire came off in my hand. Reconnected the ground wire and secured it reeeaaal good. That took all of about 2 minutes. Spent the rest of the day burning fuel and enjoying the water!

Thanks for all the ideas.

Paul J
1973 B28 - PALADIN

Ya gotta love it when you plan your day around working on fixing a problem then in 1st 5 minutes your done.... What to do now.

Use boat, great idea!