I am ready to give up on my gt40

[kmarine]

We have a1996 gt40 For many years this boat has serviced us well. Unfortunately two years ago We had to replace the engine. After much research we were able to find a rebuilt one. After installing The engine started surging at 2800 rpm like going into limp mode. we have just replaced the computer with a friend who is a ford mechanic. Distributor pickup coil map sensor throttle pos sensor and all fuel related parts. temp and oil and finally a ecm. I just picked up the boat from the Nautique dealer who told me I had a bad Ecu . They have gone through the sensors as well swapping out parts. The only sensors not replaced at this time is air temp and knock sensor. Has anyone tried to isolate and bypass sensors on the ecu to narrow thing down. I am ready to dump the thing as I have about $4000 in new parts. I am about to return to old school points and carb. Any suggestions are appreciated. Thank you all for your ideas. I am ready to lose it.

[Quinner]

Have you posted on www.CorrectCraftFan.com?? Lot's of GT-40 Guru's over there and there is also a great thread called GT-40 Poor Mans Diagnosis or something along those lines.

[kmarine]

I have read the thread in the past, nothing that has transpired from them. Just heard from my friend at ford racing he thinks we need to test the resistance on the (I think) he said #24 Pin on the wiring harnes. He Mentioned a diode issue. and a series of sensors which will trigger slow mode. At this point We are scratching at any advice we can find. as a former marine mechanic, I have been trouble shooting marine engines for 30 years and This is by far my largest gremlin. He Plans on coming tomorrow when I get off work. We may have to jump that section of the wire loom if it is not within spec.

[zoah]

Like it is going into limp mode or is?

How does the boat behave under 2800r?

Will the boat go above 2800rpm?

Can you post a video of the behavior?


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[kmarine]

After two years of searching and going to numerous mechanics I have traced it down to the #24 wire grounding out at the pressure switch This switch was previously replaced with a defective one. Thank you all for your advice.

[zoah]

I had my boat apart and had the oil pressure and oil switch wires flipped. It took me a lot longer to figure out than it should've.

I wasn't aware of how the boat behaves in SLOW as I've never experienced it before.




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[kmarine]

Yes, the service manual is vague as to how the sensors look. I spent hours looking at photos of engine zooming in and out to see if something was in the wrong spot. the manual give a schematic of the type of sensor, but when you have three temp sensors two oil sensors. knock sensors etc. you are unsure which one is correct especially after a major overhaul there the engine came out of the boat. NOT TO MENTION DEFECTIVE PARTS OUT OF THE BOX.

[Bhenry27]

Where was the oil pressure sensor located?

[kmarine]

the oil pressure sensor and oil pressure switch is behind the fuel control cell attached to the engine block with a t fitting.