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My ‘96 Sport Nautique with EFI GT-40 (approx 750 hrs) has started an interesting activity that I can’t seem to figure out. I’m interested an any ideas that I can dig into deeper.
At any speed the engine will quickly drop 500 rpm (consistent drop) and run at that new level for 5 to 20 seconds and then it will recover on its own. Again it will do this at any speed and with and without pulling someone or two behind the boat.
This has been happening for the past 5-6 times out on the water (total 10-12 engine hours). The frequency of the rpm drop is getting more frequent each time out. It originally would happen once every couple of runs. Now it’s happening a couple times each run (probably twice a minute). Additionally, the last few times out the boat has started struggling to idle without stalling. In fact, now I have to put the boat in gear immediately after starting it or it will stall.
I assumed this issue would be easily diagnosed and fixed; however, I have had the boat to both a Nautique dealer and a MasterCraft dealer and neither could replicate the issue (hard to fathom) and didn’t fix anything. They did verify that the fuel psi is 40-38, but remember that’s when the boat is running great.
On my own, I have replaced the following with no help at correcting the issue.
- Fuel line inside of the FCC
- Fuel filter
- idle air control valve (have tried both NAPA and FORD OEM part)
- spark plugs
- spark plug wires
- distributor rotor
- distributor cap
- new battery
Any other ideas?
At any speed the engine will quickly drop 500 rpm (consistent drop) and run at that new level for 5 to 20 seconds and then it will recover on its own. Again it will do this at any speed and with and without pulling someone or two behind the boat.
This has been happening for the past 5-6 times out on the water (total 10-12 engine hours). The frequency of the rpm drop is getting more frequent each time out. It originally would happen once every couple of runs. Now it’s happening a couple times each run (probably twice a minute). Additionally, the last few times out the boat has started struggling to idle without stalling. In fact, now I have to put the boat in gear immediately after starting it or it will stall.
I assumed this issue would be easily diagnosed and fixed; however, I have had the boat to both a Nautique dealer and a MasterCraft dealer and neither could replicate the issue (hard to fathom) and didn’t fix anything. They did verify that the fuel psi is 40-38, but remember that’s when the boat is running great.
On my own, I have replaced the following with no help at correcting the issue.
- Fuel line inside of the FCC
- Fuel filter
- idle air control valve (have tried both NAPA and FORD OEM part)
- spark plugs
- spark plug wires
- distributor rotor
- distributor cap
- new battery
Any other ideas?
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