1997 GT40 suddenly quits intermittently

[boneflier]

The diodes are 1N4001. They are very common and can be had at most electronic supply stores.
That's exactly what was happening, a rapid ignition cut out, and loss of fuel pumps. With no electricity reaching the ECM, everything shuts down.
Happy to report that the boat continues to run wonderfully.

[Camel_Towboat]

boneflier

When you had the problem, could you also describe this as a rapid ignition cutout - almost like someone turned the ignition off then back on in quick order? I had this issue (very occasional) on my last boat and could never figure it out. My boat never quit running...just flashed off and on. Very curious if you have found the source.

I'm experiencing the exact same issues at both members quoted above. Is the distributor replacement a simple plug-n-play, or are there problems I could create with the timing? And the diodes you mentioned, are they related to the two identical relays found on the back of the engine next to the ECM? Thank you.

[gun-driver]

Not hard at all. Utube has many videos on it.

Heres one https://www.youtube.com/watch?v=N6h0Z2dbVY4

[SilentSeven]

When you replace the distributor, you will need a timing light to set the ignition timing. Lots of vids on how do this. It's simple on the GT40 as the timing marks are easy to see. Many autoparts stores loan tools these days, I'd see if you can get a loaner timing light.

Make a note of the orientation of the current distributor before you remove. Install the new one as close as possible to the same orientation otherwise the boat won't start. Be careful when you swap the spark leads to not mess up the order. General best practice is to transfer one at a time...don't undo all of them as it's easy to mix them up.

All of this is not hard but it's not quite plug and play either.

[Peter6000]

This is a common problem in these older boats (mine is a 2002 GT40) and most all of us are now DIY mechanics,,,,,everyone tries to re-invent the wheel. Putting in a replacement relay is a simple $20 fix. If that does not work check the low pressure pump under the fuel filter cannister. You can run a long set of jumper wires from the battery to the pump. Then try starting the engine....fixed???? I had a hard time finding a switchable power wire, so I ran a lead from the always hot red wire near the relays threw in a toggle switch and now a simple 2 part engine start procedure- toggle switch, then start button and then have to remember that toggle switch always needs be off when done for the day. I think it is likely a good anti-theft fix as I have hidden toggle switch. FUNNY THING IS BOAT OFTEN STILL RUNS WITHOUT FLIPPING TOGGLE- so it is an intermittent power supply issue to the fuel pump. Easy to throw thousands of dollars in parts and mechanic bills for these intermittent electrical issues.
YOUR FORUM IS A LIFESAVER!!!!

The fuel pump is turned on by the ecu pulls the relay to ground. Easy to measure and to determine cauae.
If it's the ECU you can send it to me I fix it for you.
The cause is usually a bad transistor $15.
If you good with a soldering iron I can send you instructions.

Sent from my SM-G892A using Tapatalk

[welove]

Thank you so much for your post! I jumped the diode on my 2000 PCM GT40, and it now runs great! You saved me countless hours of searching.

For the first 17 years of our 2000 PAN's life, it started on the first push each spring. When my daughters went to college, it sat in dry storage from 2017 until 2000. In 2000, they came home due to the pandemic, and it took two weeks of searching to get it to run. One of the connectors on the high pressure fuel pump was loose. Once I found and fixed it, the boat ran great in 2020 & 2021.

In 2022, it was acting similar to 2020, but everything I did then didn't work. Your post saved me. Thank you!

[Modularman]

Hello Everyone. This is a great post. Lot's of great info on here. I have a question. I have a 1995 SN GT40 Pro Boss with a weird issue. When I recently bougt the boat, it would have an extended crank when cold, but once it started all was good. Once it was warm, it ran and started well. Then the other day I took it to the lake and it all of a sudden had a weird crank, start immediately, run for one second then shut off issue. It would do this over and over. This probem cropped up simply by towing it to the lake (so I am assuming the vibration/bouncing on the trailer made something electronic unhappy). I have replaced the ignition switch, bypassed the lanyard switch, replaced both relays, swapped the ECU for a known good one, checked engine grounds, verified battery voltage, voltage at the ignition switch, and voltage at pin 30 of the fuel pump relay lead. All test good. My boat does not have the 50 amp fuse in the battery box, fyi. As I have been going through the testing procedures over the past few weeks, I have noticed different symptoms. Sometimes I have intermittent power to the fuel pump relay, other times its dead. The new relays I bought have a power light on top of them. With the key on, engine off. the relay for the ECU has a strong consistent 12v signal. The relay that controls the fuel pump and spark will flicker and as it is flickering, you can hear the fuel pumps intermittently priming and the coil firing inside the distributor. Then after it does this intermittent routine, it will loose power and all is dead again. When the fuel pump relay is flickering, it will start, run poorly with an uneven idle, and then shut itself off. On a few occassions while cranking, I have noticed the engine will fight the starter briefly giving the cranking event a brief stall, then will start cranking again normally, like an engine that has the ignition timimng off. This is leading me to belief that I might have a PIP issue, if the sensor is feeding the computer bad data as to where the engine is running or not. Any ideas? Anyone else have this ame issue? I would think that since I have a good consistent 12 source at pin 30 with KOEO with the relay removed, and also have a good consistent 12v signal to pin 87(or whichever one gets power from the relay - i can't remember), then the inline diode to the starter solenoid should be good, right? Let me know what y'all think. Thanks in advance for any input you might have.