Unexplained Episodes of Stalling

The igniter will have a minimum coil resistance spec.   
So the best case is to actually measure the coil resistance, and add the resistor to match.

On boats where this is ignored, I've witnessed the Voltmeter actually bounce at idle in proportion to RPM. Followed in a few seasons by the symptoms above.

You're right to suspect whatever was last touched. I even like to test each replacement item or group items with a run test between procedures just to prevent troubleshooting difficulties. I like to do all the new stuff in Spring each year rather than Fall so that I can prove out each new item.

For example I won't go and replace all plugs, wires, Cap and rotor, fuel filters, or impeller and t-stat at once. I might group a few together. A bad wire or defective plug or defective new pump is easier to troubleshoot if you start briefly between replacements. Just my preference. Adds a little time but can save much more.

Could also run it from a small can - to rule out the entire fuel supply chain.before pump.

Alright....on the water....here is what has been happening...

Arrived Saturday morning, got boat in water. Started up fine. Idled to gas dock, put 10 gallons in, started up again fine, idled away from gas dock STALLED!   Started right back up, cruising at 20mph, split second loss of power, but did not stall out, made it to dock.

Let sit, and then started troubleshooting. Was able to recreate the stall several times...sometimes I would have to wait a minute or 2 for it to restart, but I could usually get it to turn over. Confirmed that ignition system was wired properly and have a coil that meets requirements of the pertronix.

For troubleshooting, I wired the positive terminal of the coil directly to the positive terminal of the battery. Starts up and runs. Have put 2.5 hours on it since, not stalling. Far from claiming victory (of at least isolating to a wiring issue between the dash and coil) becuase sometimes it would run without issue for days before cropping back up again. Also, I am disconnecting the coil when engine not started.

So, all that said. Suggestions on what else may be beneficial to test? I just planning on continuing to run it like this for rest of weekend to see if it will stall with dash bypassed entirely for ignition power. Thanks again everyone and hope everyone's holiday is going well.

1989sn2001_985 wrote: So, all that said. Suggestions on what else may be beneficial to test? I just planning on continuing to run it like this for rest of weekend to see if it will stall with dash bypassed entirely for ignition power. Thanks again everyone and hope everyone's holiday is going well.

Did you get any voltage readings? Although the problem may be intermittent, get the VOM out and see if you can detect a problem. Wiggle the ignition switch and the wiring connections.

Bryon,
Yes, intermittent electrical problems can be a real PITA. A real high end VOM would come in handy to record any voltage drops.

Bryon,
There are times when I prefer an analog VOM over a digital. Digitals unless they are the high end recording type, are slow to react so you won't see a momentary change in the reading. With an analog even the cheap ones, if you are watching, you will see a momentary blip in the needle movement.

An in-line spark tester tool like this would be helpful to you. You can leave it connected for a while, till you sort things out. Then, at least you'll know if you're getting spark when it's not starting:
https://store.snapon.com/Spark-Plug-Tools-In-Line-Spark-Tester-Blue-Point--P641969.aspx

Alright, so here's the update from this past weekend. The issue occurred more frequently than before, almost with every start. Sometimes it would occur only two or three times, and then would stay running. I did notice that now when the issue occurs I have to wait at least one minute sometimes two before the boat will turn over. This is a new development as I used to be able turn the boat back over again immediately when it occurred.

Most interesting was the final run of the day, I tried over the course of an hour to get it to stay running, it would consistently start but then stalled within a minute. Needing to get the boat back to the marina I decided I would go in 1 minute increments. So I turned it over idled away from the dock, it died. Waited two minutes and it started back up then I floored it. Surprisingly I made it all the way to the marina without it dying, but the second I brought it back down to idle it stalled on me. Waited two minutes then it started back up and I was able to make it to the dock.

Thoughts!? This just gets more and more odd. I do have a new coil, ignore module, and spark tester ready for next weekend...but really starting to think about other systems...

1989sn2001_985 wrote: ... Waited two minutes and it started back up then I floored it. Surprisingly I made it all the way to the marina without it dying, but the second I brought it back down to idle it stalled on me...

This does raise one question, are you sure your choke is consistently opening? It's an easy check.

When you give it wide open throttle, it mechanically forces open the choke, whether the choke has opened electrically or not. When you say it ran great at WOT, it made me think of this.

Prestolite instructions

Quick Update...I had the mechanic at the marina take a look at the boat today. He is stating that when the issue occurs (stalls) and when they try to restart it, it does not have spark. So, back to the ignition module we go. I have the prestolite EI (purple wire), and got a module second hand...mechanic is stating it will not spark with the replacement module. They are trying to confirm gap now for the sensor...

That said and prematurely assuming that I do not have a prestolite module replacement I can get since they are not made...recommendations?

Now is your chance to upgrade to DUI. Get 'ER Done.

Not sure on the coil, reference the instructions. You may need to reincorporate the ballast resistor.

There are multiple versions of the Pertonix FlameThrower (I, II, more?). Lots of complaintes with the Pertronix, not sure they are all legit claims though. I would probably seek the Mallory conversion then an entirely new electronic distributor.

An original [points] coil will still want power through a ballast resistor but the EI module will want 12V. This is how my 351W (Prestolite conversion) came to us wired as well as the 454 (Mallory conversion). The 351W has some kind of MSD blaster coil, probably low resistance(<1ohm), and the 454 has the original coil, probably low resistance (<1ohm). I can measure the 454 coil tonight but the ignitions systems were originally wired identically.

Basically you always want 1.5 ohm AFTER the coil (ballast + primary coil winding) AND 12V to the ignitor on most conversions. I think the damage typically done when you ditch the ballast AND use a low resistance coil (<1ohm). This will burn up both the coil and the ignitor eventually.

SNobsessed and I both have the Prestolite ignitor conversion. He does not use a ballast resistor. I can't remember what coil resistance he as. I DO use a ballast resisitor. If I have a low resistance coil and he has a high resistance coil we are both wired up OK. My boat has been this way for 15 years and his about 10 so I think we have different coils.

ANYWAY, I got a DUI for my 351W so this converted distributor is going on the shelf eventually...

Alright, so finally at the lake.

This morning I installed a new coil (linked in previous post), and original prestolite ignition module (complements of Vince at skidim), and a new rotary (just for good measure). It fired up and I had two good test runs today. Not claiming victory as the issue was so random, but have fingers crossed.

I did want to ask about the coil. I bypassed the ballast resistor as indicated in the prestolite instructions. But that thing gets hot! Is that normal? The instructions seem to indicate that a lower resistance coils with a bypassed resistor is what is needed. Thoughts?