GT40 intermittent loss of power at speed

I'd suggest that you put an amp clamp on the breaker "in" wire.   check for amperage and see if you are actually drawing more than you should be, or if the breaker might be getting weak.   the breakers do fail, so it may just be time for a replacement.    I hope that's the issue, it's a pretty easy fix.

relays are cheap, breakers not so much... verify before replacing

That 60 amp breaker is the main breaker for the whole electrical system.

If it tripped you wouldn't have been able to crank the engine over

You could crank the engine so it wasn't really tripped.

Sounds like something in the ignition system heated up and over time cooled down and when you tried to start it later it started with that component cooled down.

Or maybe you lost fuel pressure due to a relay or bad pump.that's starting to fail

If it happens again I'd be looking to see if it has spark or not when it doesn't start, to help narrow things down.

Who were you before you became a new guy again?

Keno is correct that the boat should not crank if the 60A is popped.   I missed that part in your original post.   if it does crank but the "60A" is popped, I am wondering if your ECM breaker and your main breaker are reversed? or if you are pushing a secondary breaker instead of the main.   That one is not supposed to be a 60A though.    Can you post a photo of the breaker?

If you look at the GT-40 manual in the reference section there are diagrams in Section 6 that show what fuses/breakers serve what.

There are a handful of diagrams for different functions and they're not the easiest things to follow but all the electrical info is there.

Diagram 6-2 is pretty good.

You should be able to check for voltage on both sides of the breakers to verify that they're shut.

The issue might be something that only shows up after running under a load in the water for a while

chris196 wrote: Keno, I'll do that, but I'm assuming they'll show 12v on each side as the boat is currently running fine. I'm afraid you're right that it's something that occurs under load after a certain amount of time, thus harder to diagnose.

Just have the multimeter with you in the boat for some quick voltage checks when/ if it happens again

chris196 wrote: BTW, can I change the name of the thread. It is not the 60 amp breaker.

Yes, just click on "post options". A drop down will come up. Click on "edit".

Well there was this post in the poor man's GT40 diagnosis.
Sounds similar:

1997 GT40 with approx 700 hrs.

Symptoms: An otherwise perfectly running engine suddenly dies and won't restart. Turns over but won't catch. An hour or more later, starts and runs fine. Later dies and won't start again.

Solution: Bad Ignition Module or TFI(Thick Film Ignition).

Replace TFI by removing it from the heatsink. These TFIs come in four flavors - distributor mount and remote mount, in grey and black. Make sure you get the remote mount, grey one - referred to as "Remote Mount Gray TFI-IV 'Push Start' ICM".

Update.
Got a loaner fuel pressure gauge from autozone.
Key on, engine off about 8-10psi. I hear the low pressure pump prime up, I'm assuming the high pressure pump goes only when engine running.
Start engine.
At idle I see about 36 psi.
slowly increasing rpms to no more than 2000, I see about 32-34psi.
From what I read I should have about 40 psi.
So maybe something in high pressure fuel circuit.

But, that doesn't explain the scenario where it died and wouldn't even restart. It appears there's enough pressure to idle fine.

While at autozone, I picked up their OEM brand of TFI for $55.

Thanks for the help.

Here it is-----
Keith was the module you replaced grey or black?

I was working on my boat today getting it ready for the summer and while inspecting my TFI module (was going to re-apply heatsink compound) found that it was a black module. This had me initially thinking somewhere along the line it must have been replaced with a incorrect module. The main difference between the black and grey modules is that the grey module sets the dwell while with the black module the computer controls the dwell.

The GT40 manual in the reference section (3F-13 page 222) species the use of a black CCD (computer controlled dwell) TFI module. This led to some research and I found what I think is the correct answer. I will confirm this in the next few days at my Ford parts dealership but it already looks conclusive from this article.
TFI Modules Grey or Black

from this article:-

"Since these two TFI systems are so significantly different, yet so similar in appearance, parts application problems will inevitably occur. A gray Push Start TFI module will plug right into a CCD system, and vice versa. To make matters worse, parts books are often incorrect on TFI module applications! With the incorrect TFI module installed, the vehicle will run, but driveability and MIL (malfunction indicator lamp) problems will result. For instance, if a gray Push Start TFI module is installed in a CCD system, the computer will not be able to control ignition dwell, and the MIL will illuminate with memory codes for the IDM circuit set, as the gray TFI module is incapable of generating an IDM signal to the computer. If a black CCD TFI module is installed in a Push Start system, dwell will remain fixed, since the SPOUT signal duty cycle never changes. If in doubt about which TFI module belongs on a particular vehicle, consult the ignition system wiring diagram for the vehicle. If the wire going to pin #4 on the EEC-IV computer comes directly from pin #4 of the TFI module, it is a CCD system. If not, it is a Push Start system."

These should be the correct part numbers for the GT40 TFI
Remote Mount Black CCD "Computer Controlled Dwell" ICM

Motorcraft - DY1077 (supercedes DY679, DY667, DY645)
Ford - 5U2Z-12A297-D (supercedes F1PZ-12A297-A)
Wells - F139
Niehoff - FF413
BWD - CBE40
Standard - LX-241
NapaEchlin - TP29
Delphi - DS10056
Transpo - FM544

Well dang, I didn't read far enough in that thread.
Looks like I need the F139.

Ok, back to the store.
BTW, it ran fine with that module, but I'm not going at load either.

do you think my fuel pressure numbers look suspect?

Ok, well I confirmed the F139 from autozone is not the right TFI.
They were kind enough to switch out my F125 for an F139 and now boat won't start.
STarted and ran fine with the F125.
Unless they had them in the boxes wrong, I'm going to say the F125 is the right one.
Not sure they'll switch that out for me again.

I understand what you're saying about starving for fuel. But, I don't think it's because of getting gas from the tank to the FCC canister. All the things you're describing would affect that. And that was the failure I had 4 years ago when it was my low pressure fuel pump. I know what that feels like. This isn't the same.

I'll be running at speed and there is just a momentary loss of power. I mean like a second or 2 blip, then back to normal.

But, at this point I will check anti shipon. I'm pretty sure my boat does not have an inline fuel filter. Fuel filter is inside the FCC.

I need to redo my fuel pressure measurement.
If you look on page SP-6 of the PCM Engine Owners Manual (1995-2001) it says to remove the vacuum hose from the pressure regulator before testing. (note 10).
I didn't do that, so I'll have to retest.

But first, I've got to get a functioning TFI back on there.
That was probably a wild goose chase.

On the bright side, I've become very efficient at changing out TFIs on a GT40.

I'm back and not with good news.
I was going to lake test the boat today, but decided to make sure everything was still running fine in my driveway before making the trip. No joy. Engine cranking and won't start.
I pay with the ignition and notice I am not hearing the fuel pump pressurize for that 1-2 seconds when I turn on the ignition.
I checked the voltage at pump and nothing, which makes sense.
I then took off the relay and checked the terminals there. I see just over 3V on terminal 30 & 85. Terminal 30 is coming from the 20/15 amp circuit breaker. I say 20/15 because the diagram has a 20, my boat has a 15. I've seen references of it being changed at one point by PCM.
Now, I check the voltage on both sides of my 15 amp circuit breaker and I see that same 3.1V on both sides. But, I see 12V on both sides of my 60 amp breaker. So, somehow between those 2 I'm losing voltage. Maybe a bad ground?

When I look at all the diagrams in the service manual, I do not see the 20/15 amp breaker involved in any other circuit, but I could be missing something there.

I'm assuming it's not the breaker itself as it shows the same voltage on both sides.
But, there is play in the breaker button. I can depress it slightly. That is not the case with my 60 & 12.5

When I previously had the boat running I did read what I believe to be proper fuel pressure numbers at the schrader valve.

And I guess the whole TFI thing was a wild goose chase.

Any thoughts are appreciated.